Have sharp pain behind left ear at back/mid of head for past few days but today's worst. pinched nerve? what could this be? should i take a motrin?

You may need a good: A good doctor for the long haul is what you need in order to help you with your problems. I doubt that you have a pinched nerve. Tylenol (acetaminophen) is a good all purpose pain medicine. If it does not control your pain well, then you may take a Motrin but not for more than once or twice as it can cause ulcers in your stomach. So you will be best served by having a primary care doctor whom you can go and see.