What could this be??

[Synirr]

My little oscar appears to have some sort of sore on his mouth. Is it just a bruise? Maybe he ran into something? From what I can tell, it looks like a black spot (which wasn't there before) with a little red sore to the side of it.
I tried to get a good picture of it, but of course failed miserably because this little guy never stops moving... he's temporarily in my 5 gallon hospital tank so I can medicate him.

Edit: Please ignore the crappy plants... they come from my LFS that way

 

[fufanu360]

he probably just bumped into something, they tend to do that alot