While tension headaches are unlikely to occur on just one side, it has been known to happen. Of course, you might want to talk to your doctor about it because there could be an issue of a pinched nerve or something like that. It's always good to just rule those things out.
I hope you get some relief,
Dx: Chronic Daily Migraines & Chronic Depression
Daily meds: Trazadone, Norpramin & Cymbalta
PRN meds: Tylonal #3