I've got what looks like a burn on my right wrist... it's about 1" x 0.2" and looks just like any burn I've ever had. I even "popped" it and got the clear fluid out... just like a burn. Here's the thing, I can't remember burning myself at all. I don't smoke, haven't cooked anything in a few days etc.
Being paranoid I'm worrying about some type of bacteria. I cleaned out a little in-ground pond thing in my back yard this Sunday and removed it. It'd been untouched for 5 years and was full of nasty water/muck. If it doesn't get any better in the next day or two I'll go see a doctor.