I have a slight hump at the base of my neck too, but I thought it was just bad "computer/desk posture"! Now I'm wondering if it may be related to my facial nerve pain?
I also have a pretty sizable lump/hump looking thing under my armpit area and went to a surgeon to get it checked out and he didn't even do a CT Scan, MRI, or anything. After observing it and asking me a serious of questions (did I have an infection or sore on the arm that recently healed, fever, illness, etc., he knew immediately that it was nothing. It ended up being just a swollen sweat gland with some fatty tissue (HEY NOW!
BUT I was immensely relieved to get it checked out.
Have that hump checked out. It may be something to delve further into, or it may be nothing like mine was.