Painless lump under the skin of my armpit. i can feel it on the surface of the skin. it bleeds when i poked a hole.looks like regular skin but darker?

Lump in armpit: If you shave or wax there, it may be an ingrown hair that has caused a small collection of oil/skin that you can feel, like a pimple. It is common in that location. Try soaking it for 20 minutes or so, a couple times a day, to see if it comes to a head so you can get it to open up and drain. If it is red, tender, a doctor can open it for you.