doesn't look bad could be a parasite but shouldn't be a problem for know do you give it feeder fish ? mabye make sure all feeders a clean other then that doesn't seem bad if it gets worse then you may have to treat it but for know it looks like nothing
I would say try salt first considering catfish can be pretty intolerant of medications. I would add a tablespoon of salt per 5 gallons and increase the temp a bit.