Hi. I Have Had A Painless, Wiggly Lump For The

Hi. I have had a painless, wiggly lump for the past year and a half in my armpit. I showed it to a dermatologist back then but he said it's harmless and may go away on its own. However, just 15 days ago, it became red, painful and became bigger. I showed it to a GP who told me it's a cyst and is infected and precribed antibiotics for 7 days. In this period a whole lot of pus came out of the cyst's head, it reduced in size and then he extended antibiotics to 4 more days. i'm on the 10th day. The size has decreased a lot but i still feel a wiggly lump like before. The skin color is getting much darker and looks lifeless. Please suggest what I should do. Btw, i missed 3-4 doses after the 9th day which i'm having now. Thanks