Fortunately, the CARES act suspended the RMD requirement for 2020, so you won't be penalized. You simply have two withdrawals in 2021, and you will pay regular income tax on them.
(Normally, yes, there would be a penalty for missing an RMD. You would not amend your prior return, because you only report what happened in that year on that year's return. You would report the missing RMD in the year you learned about it and calculate the penalty, but you can request a waiver of the penalty for cause, on a special form that may require you to file by mail instead of e-filing. But ignore all that for 2020, you are off the hook.)
