It could be any number of things. have you ever had gout or been diagnosed with it?
It could be a benign tumor too, there is a medical term for this but it escapes me at the moment. I had one on my cheek near my ear and I had it removed with no trouble. Are you sure the feeling ill is from the cyst like tumor on your neck? How long has it been there and when did you first notice feeling ill? it could be totally unrelated but Ii would suggest you see your doctor about it as soon as you can to rule out any more serious problems.
Sorry about the misspellings and errors:) I have had a long day.
You have many glands and lymph nodes in that area. I suspect you may have an infection going on some where. Please see your PCP and have this checked out.