I just had the same thing. Mine was red and started like a pimple then grew to the size of a grape or the like within a few days. It got painfull too. Went to the dock and it was a oil. Doc put me on antibiotics....the alt to cutting it open and draining it. But now after about 2 weeks the boil has shrunk to almost nothing...kike the doc said would happen but now I have some kind of cord or string-like thing around the same spot......scarring the S outta me!! It feels and looks like a tendon....but I'm pretty sure there aren't tendons in the armpit. If all you have is a boil you'll be ok. Just go see the deck and they'll either lance and drain it or put you on antibiotics and let it take its course. Hopefully you don't get the same sord-like thing that I have......has me pretty scared wondering what the heak it could be. I def wouldn't try to pop it yourself.....you can goto youtube and see some nasty vids of people doing that. Id rather leave it up to the professionals. Hope this maybe helped a bit.
I to have the same thing. It started out like a pimple, very painful and red then it went down but still stayed a hard bump the doc had me on antibiotics which seemed tom help temporarily but once I had been off them for a few days the lump stayed but now has some sort of string like thing running from it I'm assuming and it lead down to my arm. I am extremely concerned. My mom has said she thought it could be a gland or lymphnode of some sort. I have had it checked out and they prescribed me an antibiotic but I'm waiting to take it as I felt very rushed while I was there and I would like a second opinion.