The word lump is a very general, undescriptive word. With such a lack of description, one cannot give you a definite answer. If you want a proper opinion, then get a proper examination...in person with a professional.
A lump doesn't point to one specific diagnosis. This description could be anything. It could be a muscle knot, it could be a growth of tissue, it could be something else. Get it looked at by a good...
It may be that you have an infected hair follicle, oe a swollen lymph node. Other possibilities exist, as well. The best course of action would be to have it checked out by a doctor.