Resolution mismatch-can’t pull up system preferences

Long story short-I used an old tv monitor as the external monitor for my Mac air. I made it the main display bc it is bigger. I was playing with the scale and changed it to 1080 just to see what would happen. Now the monitor says “Resolution mismatch! Change device’s resolution!” Well, I can’t figure out how to do it because it’s the main display monitor. Every time I try to go to system Preferences, I can’t get the options to pull up because, I assume, they’re trying to pull up on the main monitor which is black with the message on it!

I've tried disconnecting the monitor and changing the scale. It appears to work, but when I plug in the monitor, it reverts to this message. Now what??