<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>0007 - Disclosure - Nature of Business and Going Concern Assumption</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

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</LabelSeparator><Level>1</Level><ElementName>VKIN_NotesToFinancialStatementsAbstract</ElementName><ElementPrefix>VKIN_</ElementPrefix><IsBaseElement>false</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Notes to Financial Statements</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>VKIN_NatureOfBusinessAndGoingConcernAssumptionTextBlock</ElementName><ElementPrefix>VKIN_</ElementPrefix><IsBaseElement>false</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="From2013-01-01to2013-03-31" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;The Company was incorporated under the laws of the State of Florida
on May 3, 1989 as Sparta Ventures Corp. and remained inactive until June 27, 1998. The name of the Company was changed to Thermal
Ablation Technologies Corporation on October 8, 1998 and then to Poker.com, Inc. on August 10, 1999. On September 15, 2003, the
Company changed its name to LegalPlay Entertainment Inc. and on November 8, 2006, the name of the Company was changed to Synthenol
Inc. Effective November 3, 2008, the Company merged with and into a wholly-owned subsidiary, SinoCubate, Inc., which remained the
surviving entity of the merger. SinoCubate was formed in the State of Nevada on September 11, 2008. The merger resulted in a change
of name of the Company from Synthenol Inc. to SinoCubate, Inc. and a change in the state of incorporation of the Company from Florida
to Nevada. On June 13, 2012, the Company changed its name to Viking Investments Group, Inc., and effective July 16, 2012, the Financial
Industry Regulatory Authority (&amp;#147;FINRA&amp;#148;) approved this name change, and the Company&amp;#146;s ticker symbol was changed
to &amp;#147;VKIN.&amp;#148;&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in; text-align: justify"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;Since November 2008, the Company has sought to enter into contractual
arrangements with entities that allow the Company to either purchase outright the assets and/or business operations of such entities
or to enter into business arrangements, such as joint ventures or similar combinations with such entities to manage and operate
such entities.&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in; text-align: justify"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;On August 29, 2011, the Company acquired from Tom Simeo, the Company&amp;#146;s
Chairman, Chief Executive Officer and President, Viking Investments LLC, incorporated in Delaware (&amp;#147;Viking Delaware&amp;#148;)
for a nominal value of One Hundred Dollars ($100). At the time of the acquisition, except for a lease obligation related to the
Company&amp;#146;s office, Viking Delaware had no assets and no liabilities. The lease expired in the year of 2011. Also in 2011,
the Company began providing incubation and consulting services to emerging market companies. Commencing from the third quarter
of the year 2012, the Company is no longer a development stage enterprise and began generating revenue.&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in; text-align: justify"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;On June 29, 2011, and on August 29, 2011, Viking Investments Group,
LLC, a company controlled and managed by the Company&amp;#146;s Chairman, Chief Executive Officer and President, Tom Simeo, incorporated
under the laws of The Federation of St. Kitts and Nevis, (&amp;#147;Viking Nevis&amp;#148;) sold 100,000 and 466,813 shares respectively
of China Wood, Inc., publicly listed in the United States with the ticker &amp;#147;CNWD&amp;#148;, (the &amp;#147;China Wood Shares&amp;#148;)
owned by Viking Nevis, in exchange for 1,912,000 and 12,569,420 newly issued restricted shares of SinoCubate respectively (the
SinoCubate Shares&amp;#148;). By August 29, 2011, Viking Nevis completed the purchase of the China Wood Shares by having delivered
a total of 566,813 shares of common stock in China Wood, Inc. to the Company. The China Wood Shares were registered in a Form S-1
Registration Statement declared effective by the SEC on April 7, 2011. The China Wood Shares are subject to a &amp;#147;Leak-Out Provision&amp;#148;
whereby only a certain amount of shares can be sold per month up and until the first anniversary of the effective day of the aforementioned
registration statement, April 7, 2012.&amp;#160;&amp;#160;The Company accounted the exchange of shares under ASC 845 - Nonmonetary transactions.&amp;#160;&amp;#160;Due
to the fact that the exchange of shares had no commercial substance, the Company recorded the China Wood Shares as a long-term
investment and valued the shares at the carrying value on the transaction date.&amp;#160;&amp;#160;The shares were fully impaired as of
December 31, 2011.&amp;#160;&amp;#160;See Note 2 and 4 for additional information.&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in; text-align: justify"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;On September 26, 2011, the Company entered into a non-competition
agreement with Viking Investments Group LLC, a Nevis and St. Kitts corporation (&amp;#147;Viking Nevis&amp;#148;) whereby Viking Nevis
agreed to cease all operations in China and transfer all rights, title and interest related to its business in China to the Company
and its wholly owned subsidiary, Viking Investments Group LLC, a Nevada corporation, in exchange for the Company issuing registered
shares of its common stock under a Form S-8 to Viking&amp;#146;s staff.&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in; text-align: justify"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 10pt Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;The Company incurred recurring losses and had a net loss of $85,986
and $101,146 for the three months ended March 31, 2013 and March 31, 2012 respectively. As at March 31, 2013, the Company&amp;#146;s
cumulative deficit and stockholders&amp;#146; deficiency amounted to $5,983,865 and $136,932 respectively, and the Company had a cash
balance of $226 and a working capital deficiency of $145,267. The Company&amp;#146;s ability to continue as a going concern is dependent
upon its ability to generate future profitable operations and/or to obtain the necessary financing to meet its obligations and
repay its liabilities arising from normal business operations when they come due. Management has no formal plan in place to address
this concern but considers that the Company will be able to obtain additional funds by equity financing and/or related party advances;
however there is no assurance of additional funding being available.&lt;/p&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>Note 1. Nature of Business and Going Concern Assumption</ElementDefenition><ElementReferences>No definition available.</ElementReferences><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Note 1. Nature of Business and Going Concern Assumption</Label></Row></Rows><Footnotes /><IsEquityReport>false</IsEquityReport><ReportName>Nature of Business and Going Concern Assumption</ReportName><MonetaryRoundingLevel>UnKnown</MonetaryRoundingLevel><SharesRoundingLevel>UnKnown</SharesRoundingLevel><PerShareRoundingLevel>UnKnown</PerShareRoundingLevel><ExchangeRateRoundingLevel>UnKnown</ExchangeRateRoundingLevel><HasCustomUnits>true</HasCustomUnits><IsEmbedReport>false</IsEmbedReport><IsMultiCurrency>false</IsMultiCurrency><ReportType>Sheet</ReportType><RoleURI>http://sbat.com/role/NatureOfBusinessAndGoingConcernAssumption</RoleURI><NumberOfCols>1</NumberOfCols><NumberOfRows>2</NumberOfRows></InstanceReport>
