I have the Exact symptoms you do, including the knobby bit. My chiropractor suggesting it was occipital neuralgia. I went to see a deep tissue massage therapist about some neck pain I have been having and she massaged my mouth and where my skull and neck meet. I felt 75% better after that. I haven't had a headache in 4 days. I just got back from another chiropractic appointment where he adjusted my c2 and both told me the same thing - even though the pain is in the left side, my right side is so tense it is causing my left to compensate. Hopefully a couple more appointments to each and I should be fine. So, whilst I believed I had ON, and had your exact symptoms, it's not seeming to be anything more than a temporary problem with my spine and jaw. Obviously, I don't know how things will end up, but right now, for the first time in months, my days are almost back to normal and are largely pain free.