What causes pain and throbbing in the back of the and neck and forehead?

Muscle pain. Pain in the back of the neck/head as well as forehead can be due to muscle pain; which can be due to posture as well as strain due to over activity. You could try applying ice on the back of the head and see if that helps. Also, try tylenol (acetaminophen) or advil if you are not allergic and can take them safely.