It started yesterday afternoon, near the top of my head, and continues tonight. It doesn't seem to be a traditional headache. More like a muscle cramp in a tiny adductor muscle that extends from neck to top of head, allowing the head to nod. Moving the head, clamping my jaws, etc., gives a sudden sharp stab to my head. Rubbing the spot doesn't help, and when I take my hand away, it stabs again.
Stress, I suppose. It's always stress. I need to completely relax and bore out all the crud that's accumulated in my barrel (so to speak).