Hi. Back in November, I noticed that I had a blister in the middle of the sole of my left foot. A small one, and it was really dark. I figured it was blood in it..thus a blood blister. I left it alone and it stayed for about 2 weeks. Then, when I was getting out of the shower I noticed a little blood in the shower and saw that it had burst. I felt relieved although it never hurt at all. Then a couple months later another one grew on the right side of the sole of the foot, but this one got bigger and bigger and bigger. It was uncomfortable, soon it had me unable to walk properly. I had to limp. I debated on popping it but bought antiseptic and bandages and popped it after a week. once I popped it it was sore (to be expected). It is healing now and I m growing new skin. Now, I noticed my left foot has another blister on it last week..small in size, but about a few days ago it has turned into a black mole...or really dark brown. I am worried it may be cancerous. The edges are not totally irregular but slightly on one side. I am worried because for the longest time..years I would plant my feet directly in front of my space heater. I no longer do that now.