Have a cysts on my underarm i am on an antibiotic but will it come to a head and need to be drained?

Deep or superficial?: If its up in the skin and moveable it is most likely just a skin cyst. If it is deeper in the armpit between the muscles it may be a lymph node. These can feel like a grape deep under the skin. If infected cyst, it may come to a head and break with hot compresses or need drainage. If deeper and not resolving get mammogram and breast exam to rule out a breast ca that spread to lymph node.