What Causes A Lump On The Back Of Neck?

I have a lump on the back of my neck on the right side that has grown a little bit since I noticed it about a year ago. It s about the size of a quarter. It doesn t move around and hurts if you push on it. Sometimes it just hurts too. It is close to the base of my neck where the bone sticks out. About a couple inches above. Should I be concerned?