Overcontribution to Roth IRA. What should I do?

Last year, I did a prior year contribution to my Roth, and overcontributed. I realized this before investing any of it, so I tried to correct it by doing a withdrawal. I never filled out a Return of Excess form.

This withdrawal amount is now reflected in my 1099-R, with box 2a ("taxable amount") empty and box 2b ("taxable amount not determined") checked.

My understanding is that the withdrawal is not taxable anyway because I was not withdrawing earnings. But, I can't ask for a return of excess now because the amount is now correct (?).

What should I do? Thanks in advance.