I have a big painful lump like thing in my armpit. it restricts my arm movement and i have constant pain in it?

Doctor can examine: Lumps in the armpit skin of a young adult can be due to ingrown hairs or blocked oil (sebaceous) glands. Occasionally, they are blocked pores, filling up with dead skin cells. If a lump hurts, it may be infected and would need antibiotics or need to be cut open by a doctor, depending on how it looks. Lumps deeper in the armpit may be enlarged lymph nodes, which can be infection or rarely cancer.