What Causes Tenderness On Crown Of Head And Neck Pain After Injury?

Hit top of head in to roof of car jarring neck and top of head is very painful Notice that scalp is very tender, neck little sore from jarring, and pain in middle of left arm and left calf, did not have prior to hitting curb with car I was riding in. I am diabetic, should I go to Dr. or give head and scalp pain a chance to go away. This happened about 5 hours ago.