Got hit by something or somebody caught him and let him flop around around on the carpet/ground. 

That's all?  Looked pretty nasty. I thought ght it was some kind of disease or something 

Fish are spawning or post spawn a lot of areas right now, puts a lot of stress on them and they'll develop sores and some fish will die as a result of the rigors of the spawn. 

And if you let them flop around in the boat or on the ground it will rub their protective "slime" off which weakens their immune system and makes them develop diseases or get infections in the areas that rubbed off.  It can sometimes kill them. 

I see what's wrong with it, it's not in the grease lol.

 

It's just soar's from spawning or a skin infection from its slim being rub's off, it will be fine.

Looks like it went 12 rounds with rocky Marciano

Most of the fish I caught lately from shallow got those kind of skin/scale disease. These fish were from around tree and brushes. Not a pretty fish at all.