Strange Pimple and lumps on the back of the head torwards my neck.

Hello,

I have very strange problem. I have a strange lump on the back of my head torwards my neck on my scalp. There are aslo 1-2 pimples that have formed scabs and arepainfull. I asked a coworker, who is a massage therapist, to feel it. When she applied mimimal pressure I felt a slight pain and asked her to stop and she stated it didnt feel right.  I first noticed this issue about 1 1/2 years ago. The lump does reduce in swelling and the pinples and pain go away but in a few months they will resureface from the left side of skull, above the base, and the right side. Im getting worried about it  because every few months or so it comes back. I have never, to my knowledge, had any head injuries or concusions. Any advise would be greatly appreciated.

damaris