What Causes A Swollen Mass On Bottom Neck Causing Severe Pain?

i have a sponge like mass almost feels jelly filled bottom of neck where your shoulders meet to the left of spine. I have been having headaches a do alot of rubbing my neck cause its painfull sometimes would get a pinch like a pinched nerve. but the swelling is about the size of your palm. Should I be concerned or should I go to my neck doctor or regular doctor?