When I filed my taxes I had not received the 2nd stimulus and claimed it on my taxes. After submitting taxes I received payment. What is going to happen?

Most probably the IRS will make the necessary adjustments before releasing the refund. If they don't, you'll have to amend your return. 

How do I amend my 2020 return?

Thank you for responding.

One more question, how will I know if I need to,  or when to amend or if I just leave it alone?

You can leave it for now. You have to wait until your return has been fully processed and you have received your refund.

Ok thank you. So the irs will still issue the full amount, and then I do the amend? And just return the amount for stimulus? Or will they issue return minus stimulus? IRS accepted return on 2-10 and my status still says processing.

More than likely the IRS will subtract the stimulus that crossed paths with the filing of the return.