It depends. You’ll have to wait until the IRS processes your return.
If the IRS rejects your return, you can adjust your stimulus amount and re-file.
If the IRS accepts your return, it’s possible they may adjust your refund. In that case you won’t have to do anything. The IRS sent out the stimulus money so they have a record of how much they paid you so they will probably adjust your refund. However the IRS has not started processing returns so nothing has come back.
If your return is not adjusted, file an amended tax return to pay back the extra stimulus.
Click here for help: How do I amend my 2020 TurboTax Online return?
New - If you filed and claimed the Recovery rebate credit but already received the full Stimulus payments you can call it back and update your return so it isn't delayed