Talk to Dermatologist on Armpit Lumps (i Dont Know If Those Are Called Lumps)

I was having pain there, when i checked. It was more of a hard bump/lump like structure under the skin. It pains a lot, even if i touch it slightly. It was there one time before too but after several days it was gone. Now its on both of my arms, and it pains the double this time. Please do tell me, what i can do or from which doctor i can get checked (like dermatologists or general practitioner etc)