Facial Swelling, Red

Question
My rat had a swelling on the one side of his face for about a week, from research we could do online it looked like a misaligned jaw.  He was not losing any weight and was playing and eating normally.  Two days ago the swelling "broke" through the skin.  It looks sort of like a tumor and has a bad odor.  He is still eating but seems to be a bit uncomfortable.  He still wants to come out of his cage and play.  There is no pus coming out and no visible bleeding.  What could this be, and what can we do.

Answer

Sounds like an abscess. If you gently apply pressure, does pus come out of it?  

Tell me where exactly this lump is located:
By his ear on his face or lower, toward the mouth?

What I need for you to do for starters is to apply a warm rag to the area to help whatever is in there come to a head and press on it gently after a bit.  If you get anything out, clean the hole out with clean warm water and apply some antibiotic ointment.  

Let me know where it is located though....and I will tell you now that he more than likely may end up needing a vet for oral meds. If you do not have a vet I can help find one for you that treats rats.

Hang in there and try not to worry....I know they can make us sick to death with worry but we will get him on the right track again.  

Is he eating and drinking ok?