Provided wrong answer to question "did you receive a stimulus check". Fogot that we got a 1200 payment in July. What to I do now.

If you have already filed your 2020 tax return, the IRS will make the correction for miscalculated Recovery Rebate Credit amounts.  You do not need to do anything at this time.  Wait for your return to process and you will receive a letter from the IRS explaining the changes to your return.  

Here is a link with more information on Recovery Rebate Credit corrections.