1. Check your 2021 tax return. The excess is not allowed to be excluded from your income and must be added back to your line 1 taxable income. Any tax software should have detected the excess contribution from the items in your W-2s box 12, code D or code AA. The tax software should have told you that you have an excess and suggest you remove it. If you told the software you would remove the excess and you didn't, then you do need to prepare an amended return to change your answer. The $2K excess is added to your taxable income so you will owe a tax payment with your amended return. However, if the excess was detected and already reported with the excess added to line 1, you don't need to do anything more.
2. There is no ongoing penalty for an excess 401k contribution. It is just over. You will pay tax on all your withdrawals when you retire, even though you already paid tax on the $2K excess contribution. That's the "cost" of the error, paying income tax twice on that $2000 excess amount.
