If you messed up your monitor with a magnet…have no fear, grab a high rpm drill.. strap a couple of magnets on it. (Hard drive magnets work great. You’ll need one at least as powerful as the one that messed up the monitor.) Bring the drill to a high rpm, and point it at the monitor like a ray gun. It’ll tweak the monitor something fierce. But after you pull it away from your monitor whilst it is running, the spots will be gone. (It may take a few passes depending on the strength of the spot and magnet.) Link.
HOW TO fix your magnet ruined monitor