first thing you should do is take an appointment with a GP. it helps if you are insured, and then can go to a private clinic (or just go private anyhow).
are you sure you have pin pointed the correct part of your body?
have you had headaches, ENT troubles (ears, nose, throat). problems with lack of saliva..
again no one can really provide a blind diagnosis over the net. but answering these questions will make its easier for your doctor to find out whats going on.
have you eaten or had contact with something you may be allergic to?
with most node problems - docs do biopsies if they see the need.