My oscar has a blister in his mouth

Question
I have a 7 month old Oscar.  My daughter noticed a bump on the outside of his mouth, she called it a zit.  LOL. I thought it looked just like a small bump and it is also protuding into his muth looks like a blister.  I have noticed that he constantly picks up rocks in the tank and moves them.  I also have convict and an algae eater in there.  Is this from messing with the rocks and he injured himself he's very agitated.  Thanks for ur help

Answer
Hi,
It is not uncommon for a fish to accidentally injure it's self, much like people. It should be fine as is, but if it gets worse, or if you see anything else unusual, ask me about it as this may be a sign of a small parasitic or bacterial infection that can be easily treated.