I noticed a few months back that a pore on my arm had become a bit larger than normal, and that the skin was raised underneath. When pressed, it was mildly painful and I felt a hard mass underneath. A little alarmed, I started hot/cold compresses to bring it to a head, thinking it was simply an overlarge pimple. It took me about two days, but i finally was able to expell the mass via tightening the skin around my arm and squeezing around the pore. A large amount of pus came out, along with a bit of relief from the pain, but now it keeps filling up, and the pore refuses to shrink. Is it a cyst on my arm, or simply just an overlarge pimple? Either way, is the constant refilling of the pus chamber cause for concern and should I see a dermatologist?