Yes, you should file an amended return to report this business.
If you have a self employed business then you will need to file Schedule C to report any income you had and expense(s) that can can be applied to offset that income.
-follow these links for additional information-
Where do I enter Schedule C? - TurboTax
What Is a Schedule C IRS form? - TurboTax Tax Tips & Videos
How to Correct Federal Tax Returns - TurboTax Tax Tips ...
