Another lump by armpit?

In December I went to the dermatologist for boils and a lump under my armpit. She gave me antibiotics and told me that if the lump stayed that she'd have a mammogram done. The boils and lump went away so there was never anything set after that. She thought it was based on fungal and that the lump was a benign cyst. 2 days ago I got another lump under the skin on the same side. It feels a littler different and is hard. Idk if its just tissue because it doesn't feel like a normal lump. When this all happened I woke up with an achy shoulder. We were staying in a casino hotel and I don't know if it has to do with the fact that I used my brothers razor, the cigarette smoke or what. Cig smoke messes with my sinuses and I did have a sinuses infection a few days ago. I also slept wrong in the bed since I had to sleep with my brother. I'm 22 by the way. The skin surrounding it has a burning sensation to it.