What Causes Headache In Back Upper Side Of Head?

I have had a headache in the back upper right side of my head for a couple of weeks on and off.Sometimes it is stabbing pain and sometimes it is more of a dull pain. Jolting movements sometimes trigger it. I did hit that area of my head by accident about a month ago. Should I go see a Dr. soon or see if it goes away. Also, for the last four days I have been sleepy. thanks for your time.