it sounds like you might have a couple cysts. I've had two in that area, both right in my armpit (gross I know) but the second one hurt... and when I went to the doctor I found out it was infected. So DEFINATELY go to the doctor asap to get them checked out!
You could also be having an allergic reaction to something -
i.e. new deodorant, new clothes detergent. We also have
lymph nodes around our armpits. Maybe you have some kind of
infection. Are feeling allright or are you feeling off?
that's what I thought but then another bump appeared today, that's whats got me worried. Does it sound like something is spreading?
If it doesn't go away soon, like by tomorrow, I would go in
and have the doctor look at them. Tumors are hard and don't
usually cause pain. Maybe you got bit by a big mosquito.