About Cyst. It pls suggest what is this?

I am noticing a blckpepper sized cyst in my right underarm since some months..its sized increased in some last days but in very little amount..not much cyst is close to skin and can felt by touching upper skin and when i pressed it feels round and size is like a blackpepper..and it feels little hard.and.close to skin and the cyst have very little mouth. and there is no such pain After pressing tightly ..cheese like substance notice came out of it but in very tiny amount.after that.i tried to press it but no much pus came out of it Pls suggest what is this??? I am worried of this cyst..there is no presense of fever or any other problem after getting this underarm cyst Usually from many years but sometimes i always get puss filled cyst in underarms but it generally goes away after taking antibiotics..and pus gets drained itself.. Specially when i remove underarm hair my skin gets irritated and little boils also came after that Pls suggest me about this recent cyst.