Whats Wrong With My Bristle Nose Plec?

[450ltrtank]

ihave 2 bristle nose plecs but i have just realised that 1 of them has a big white lump on the side of its mouth has any1 got any idea to what it could be ?

 

[emmettbaby]

mouth rot for fish? I'm not sure, maybe he hurt himself in the tank and developed a bacterial infection? Might want to post in the emergency section too, just in case?

 

[JenCliBee]

Without a pic it's gonna be hard to give a diagnoses.