need help on black piranha asap

[nick the kid]

My black piranhas bottom lip has a really big sore/cuts started as two little cuts now within three days has taken over the front of his bottom lip its white looks like its eating at his bottom lip need help had this guy since he was the size of a quarter

 

[xkon]

Post a picture if you can

 

[jp80911]

keep the water clean (frequent small water change as needed), up the temperature to 82F, add salt (the aquarium salt container should have dosage information).
piranhas have very impressive healing ability, as long as water is clean they will most likely heal without any med. but doesn't heart to use melafix and pimafix if you have them