Repayment of Signing Bonus in Subsequent Year. Need help with 2020 and 2021 Taxes

I received a signing bonus of $20k in 2020.

I left in 2021 before the $20 k vested.

I repaid $18470 to my former employer and agreed not to seek the social security and medicare from the IRS.

 

I received a corrected w2c with only the following reduced:

social security wages

social security tax withheld

medicare wages and tips

medicare tax withheld

 

My wages were not decreased.

 

At this point how do I handle my 2020 and 2021 taxes?

Do I file a corrected 2020 tax form with only the 4 mentioned fields above corrected?

Do I address the $5000 in taxes I paid in year 2021?

Do I forfeit that $5k in taxes?  If that is that case, that is seriously messed up.