What did the physician tell you he/she thought it was? Sounds like not much. Is it possible to consult a Dermatologist to assess the site? A small pea size lump on your neck could be many things, and I wouldn't begin to guess.
The description would suggest that it's a swollen lymph node which is a common reaction of the immune system fighting off an infection (i.e. cold, flu, injury, recent dental care?)