Okay slow down. It showed up overnight practically?
Even with your pics it really does seem like an abscess. A swelling that now has a nice dark crusty scab?
Does it look similar to this?
Abcesses are part of rat ownership. The body walls off a foreign body (stitch after a surgery) or a bacterial infection and creates an abscess. They swell up, get a dark patch where the skin is thinner. Then a scab forms and the abscess bursts. A lot of us use warm compresses to push things along. This brings the abscess to a "head". Once it bursts you need to flush it out with a saline solution to get rid of the pus and matter. Its going to smell bad, be prepared! Everyday you have to soften the scab to remove it, then flush it out, twice a day. A rat heals so fast that the skin part will heal with the infection still inside and the abscess will just keep recurring, it needs to heal from the inside out.
