Amend

Wait until your return has been fully processed.   Sounds like you got confused between the child tax credit and the stimulus payments.

Get your information in order so you know for certain what you received and what you did not receive.

If you received the 3rd EIP payment you should have letter 6475 that tells you how much you got for the stimulus that was $1400 per person.   Those payments went out in mid-March or later in 2021.

If you received any advance child tax credit payments between July and December you got letter 6419 for that.   If you got those it would have been $300 per month for each child under age 6, or $250 per month for each child 6 or older up to age 17.

Check your own banking records for the amounts that were put in your account.   And check your online IRS account to see what it says:

https://www.irs.gov/payments/your-online-account

If you said on your 2021 return that you did not receive the stimulus money---but you did receive it---then you had an incorrect amount on line 30.   The IRS will fix that for you.   You do not amend for that.

If you entered the wrong amount for the child tax credit they will likely fix that too----but you need to wait and see what they do.

If the IRS does not make the necessary corrections, THEN you can amend.