You
MUST file your tax return. Even if you don't consider yourself "self employed" the IRS considers you self employed and you
MUST file Schedule C (Form 1040).
The income you received as 1099-Misc is your self earned income, which is not earned as a regular employee. Your net income from schedule C is also subject to SE tax at 15.3%.
How you will treat the 1099-Misc income, read:
Your U.S. Tax Return: W2 or 1099: Employee or Independent Contractor.