You will need to amend your 2019 tax return and the only change (that you've indicated) you will need to make is to your filing status and the line items that are affected by the status that you filed as compared to the change in status (amount of standard deduction you are entitled to, the information including SS# of your spouse, and anything else that would pertain to you). If your spouse filed single, however, then when the IRS runs the amended return along with his/her SS# you've provided on the amended return, they will most likely reject it because he would also have to have filed married - including MFS and MFJ - meaning that you both would need to file the same way.
