I was in a car wreck earlier, and now I have a headache. Should I go to the doctor?

[anna]

I ran into the back of a truck. I wasn't paying enough attention and they stopped fast and I ran smack into them. They had a trailer hitch, so the impact wasn't dispersed like if I had hit the bumper on the back of a car. The front of my car has a big hole where their hitch went in, and the metal behind it is bent, too. Looking at the front of my car, the hole in my front bumper is near the driver's side, so it wasn't exactly in the middle. My airbags didn't go off. I don't know what happened to my head. It might have slammed against the back of my headrest, or maybe not. I can't remember. I don't think I hit it on the steering wheel, but I really don't remember. It happened fast. This was like 4 hours ago. I felt ok until my head started hurting kind of recently and I feel sore. Could there be internal bleeding or swelling? I can't go to my regular doctor since they're closed for the day, but I feel stupid going to the Emergency Room. So what should I do? If I wait until tomorrow to see a doctor or nurse, would that be too late if something's bleeding or swelling inside? How can I determine what to do? Thanks.