I have a small, pea sized purple bump on my armpit. It is not painful, but tends to get tender if my bra rubs on it. It doesn't look like an ingrown hair, there is no head on it either. it is hard to the touch, i can pinch behind it and feel a hardness to it. squeezing it only produces blood from a pour or follicle. i have had it for about 2 weeks now, does not seem to be getting any larger, and certainly is not getting smaller. what could it be?