I just e filed my taxes and i made a mistake about the third stimulus check. i said no and i just found a record that i did receive the stimulus check. what should i do?

If the return is rejected you can make the correction and refile the return.   If the return is accepted for processing then the IRS will automatically catch the error and make the correction for you ... of course this will delay the return processing ... how long this year is unknown but last year it took MONTHS.

can i contact the irs any way and tell them about this simple error

Should i file an amendment

No you cannot contact the IRS to fix it and amending would be a waste of time and effort.   The IRS will be checking returns that have the EIP payment on line 30.  The IRS knows if they gave you that payment.   They will remove that amount from your refund and your refund will be less.   And it will take longer for them to process your incorrect return.   Do not expect a quick refund.

Thank you.  this sadly answers my question.  i had a brain mess up when i looked at my bank statements looking for the stimulus deposit.  i looked three times and still missed it.