2021 SEP contribution

My employer contributed approximately 8K to a new SEP IRA in my name, in April 2022 as a 2021 contribution. I already filed my 2021 return and received my refund prior to the contribution. Also,  in July 2022 I had to liquidate the SEP IRA as I needed the funds. I understand there is a Penalty in addition to the 10% that was mandatory withheld. I then withheld 15% federal and 4.25% for Michigan.  My questions are 1. Do I need to Amend my 2021 return?  2. Where can I Amend my 2021 return if needed. 3. What is the penalty? 4. How will I be notified of the penalty. Thank you.