bite wounds and mouth sore

Question
HELLO
My rabbit has a mouth sore on the left side of the mouth. It looks as if it were a canker sore but the center of it is black.  
Also, my rabbit has old bite wounds from a guinea pig  (they are not housed together) the wounds have been treated and are healing but they are still leaking think white pus. By the way, I feed him orchard grass, hay, and pellets.  WHAT SHOULD I DO?                  THANK YOU VERY MUCH FOR YOUR TIME

Answer
I think it would be the best if you took your rabbit to a vet.  

I'm not sure what the mouth sore is.  I wonder if it might be related to the bite wounds.  You're not clear what treatment was given for the bite wounds, but the white pus makes me think there is an infection going on.  and infections can be difficult to treat and may cause more problems down the line.  

A vet should determine what bacteria is causing the infection and appropriately treat it.  With rabbits, it doesn't seem to take much of a bite or scratch from another animal to get an infection going.

This page gives a couple stories of rabbits with infections:
http://www.ontariorabbits.org/health/healthinfo1.1.htm

And here's some more info on infections in rabbits:
http://www.veterinarypartner.com/Content.plx?P=A&A=503&S=5&SourceID=43

Make an appointment with a vet and good luck