Last night i suddenly felt a pain in my left armpit, feeling around i discovered a small painful lump, just by glancing it with my fingers it broke, and some pus/blood started oozing out. I tried gently pressing on both sides and suddenly blood stood out, the pressure in the lump lessened and i didn't think anymore of it.
Today it looks like [this.](http://imgur.com/wVfqsCB)
It's roughly ½-1 cm deep.
Should i go see a doctor?