Oh wow...poor thing. Good luck getting him healed up. I had a hard time figuring out what I was looking at, but once I turned my laptop over it all made sense lol.
It is kind of fun, I think, to nurse injured fish back to health, but unfortunately medications are so expensive. Every time I've had to treat a fish that had some sort of infection, I ended up spending more money on meds than I did on the fish in the first place. But that's part of being a responsible pet owner I guess.