Need help with white spot on puffer

[Ragtop68rs]

I have a yellow dog face puffer that has a white spot that is about 1/8" in diameter with what looks like an indentation in the middle of it. It is on his body about a 1/2" in front of his tail. For the last month or so he had been keeping his tail tight(not fanned out as normal) and curled up most of the time. He was in my 300g FOWLR but I just pulled him out last night and put him in quarintine. I've never had any disease in my tank as I always quarintine. I need help identifying this so I can figure out how to treat it. Thanks, John

 

[ThRoewer]

I don't think this is uronema. It looks more like something is eating on him, a crustacean parasite, a worm, ...
If possible look at it with a magnifying glass or better a microscope to see if there is something living at the center of the spot.
If that's the case then this may be one of those rare cases where a cleaner shrimp may be able to help.
Otherwise you either may need to pick it out yourself with some pointy tweezers or use such nasty medications as Dylox.

Though there is likely also a bacterial infection going on, so antibiotics may also needed.