Does it hurt when you turn your head or when you bring your ear toward your shoulder? The problem could be a tight levator scapulae! This is a muscle that runs from the base of your skull to the top of your shoulder blade.
It an be tricky to massage yourself without a tool, so a theracane is really helpful. Try this massage to get some relief. Do it 6-12 times a session multiple times a day for a few days!