Soo.. My rat Kurt is about 2 1/2 years old. He's an albino male fancy rat. (Red eyes and all) He's been very very healthy ever since he was a baby. He's been a little overweight thanks to me, but here's the problem.. He had a lump below his chest for about a week or two. I did some research and apparently if you move the lump around and it moves with the skin then it isn't a tumor. (Thank god) So, i'm thinking it was a cyst. About yesterday I took a look at it and it had opened completely. Mind you, this thing is about the size of a half a dime, so not huge. I don't know if it opened by itself or if he chewed it open. (He chews on just about everything) So it's an open wound now with most of all of whatever was inside of it gone. There wasn't any blood or anything, just clear liquid and a bit of puss. But, on the top of it there looks to be a little light green thing hanging from the inside. I was thinking everything was okay until I saw that. He acts pretty much the same, he's obviously older and is a little slower now, but still hyper, and he's lost a little weight. So now, i'm not too sure what to do. Anyone have any history with rats that could help me out or what I should do?

Thanks a bunch =)