What Causes A Lump Under The Skin Of Areola?

Hi I have had a half of a pea size pimple lump under the skin of my areola for two weeks, I have tried hydrocortisone and antibiotic cream but none of them help, sometimes when I use my finger to rub on the skin it can be smaller sometimes and a bit bigger the other times, do you know what it is? and what is the treatment for this? Thanks alot