If you don't have a 2019 return to do then don't do anything with the incorrect 2019 return until you see what the IRS is going to do about mess. Most likely they will send a letter asking for an explanation. At that time you can tell them it was a big mistake and to ignore the entire return.
In the meantime you still have to file the 2018 return as it is very very late now ... if you have a balance due you should pay the amount when you mail in the return to stop the penalties & interest from accruing. It may be possible to get the money you paid on the 2019 return redirected however it may take some time.
