1099-MISC

You have to report it even though it is a small amount. 

Usually, IRS treats taxpayers who receive a Form 1099-MISC as business-related.  They are considered self-employed.  You are required to pay Self-Employed taxes.  If you received this form only once in a while for some work unrelated to your main job, or if you receive it as an award or prize, you would not be treated as self--employed.  If you will be receiving it ongoing in the future, you are self-employed and will need to file a Schedule C.  For details, click here: Form 1099 misc

Since you have already submitted your tax return, you will have to wait until Feb 12 when the IRS opens the gate. You cannot return to the program to make any changes before that. 

If your return got rejected for whatever reasons, you can return to the program to report the form along with other changes.  You do not need an amendment 1040-X.

If your return has been accepted, you will have to amend your return by filing a form 1040X.  You should not try to amend your return until it has been fully processed and you have received your refund or your payment has cleared.

Beginning with the 2019 tax year, you can e-file amended tax returns. If you used TurboTax to prepare Form 1040-X, follow the software's instructions to e-file the amendment.

To see how to amend your taxes, click here: 

Steps to amend in TurboTax

How to file amendment