Hit my head very hard on a car trunk 5 hrs ago - no symptoms, but now have a sore spot on one side when i touch it & also hurts when i bend over. ok?

Could just be bruise: but of course we worry about concussion, you should see a doctor

Contusion: most likely. Put a cold pack on the sore spot so you don't get a lump, and don't take any aspirin (which can increase the bleeding). If you develop dizziness, nausea/vomiting, or difficulty concentrating be sure to see your doctor. Soreness should slowly resolve over the next few days.