Green strip at top of screen

i read some other troubleshooting descriptions and i think i figured out how it happened. i put speakers on top of the tv (which i don't usually have there) and the next day the top of the screen was green. i think this is from the magnets in the speakers...but can i fix that myself somehow, and if not, how much should it cost for something like that to be fixed at a repair shop? thanks a lot...