My fish is paralyzed.a rock fell on him about 2 months ago and sense then his ability to swim has decreased

I call this guy big Jim. He’s a cardinal tetra. And about 2 months ago I came home and found him smushed under a rock. He was okay but his fin was a little damaged. Sense then he’s been losing mobility. Yesterday he stopped swimming all together. I’m still able to feed him though. I cup him in my hand and pretty much hand feed him. I don’t want to get rid of him because he’s not dead but idk what to do