What Causes A Hard Lump Under The Ear?

Hi there I am a 25 year old male heavy smoker, and recently found a lump just under my left ear. It is about the size of a pea, maybe slightly bigger, its quite hard and slightly mobile. It isn t sore to touch but it does hurt a little when I squeeze it, after I squeeze it I can feel my pulse go through it. I don t know what it is but it has me slightly concerned, any help? Thanks.