GBR with abscess/tumor

[GuppyLover]

I noticed the side of my GBR's mouth was a bit red lately but never really paid attention to it. I was really busy today and just went over to feed them and noticed it turned into a big abscess tumor like thing. It's right under her eye to a little bit away from her mouth. I took pictures and I noticed she hasn't been eating very much lately. I didn't feed yet but when I do I am going to see if it is effecting her eating. Fiji is by far my favorite fish in the tank and I would hate to see her suffering. Is there anything I can do for her? It looks like and is about the size of a pimple.
Please help

 

[GuppyLover]

Just fed her and she is eating fine. It really looks like a pimple, white head and all.

 

[GuppyLover]

Bump. Anyone??

 

[FastFly67]

I'd pull her out and put her in a QT tank. That way you know nothing in the tank will be picking at the wound. Then treat her with melafix. Without knowing what caused it, I'd treat it as as open wound.