My friend has a similar symptom which turned out to by a lymphatic system infection. See if you can feel any other bumbs all around your neck, behind your ears, in your groin. I sometimes get lymphatic infections and use a lymph drainage cream which works very well - it is available at health food stores.
I guess the best bet is always to be examined by a physician as they will be able to assess you fully but was just a thought on possible cause.
I understand the "no insurance" problem, a lot of us have that too.
As to the lump, how long has it been there, since it is tender, I think I would try to see a doctor, I know it can be spendy, but, it is better to get things like lumps checked into as soon as possible to rule out cancer and such.
Have you done any heavy lifting in the past causing muscle strain.
Good luck, let us know how you are doing.