I was hit on my head very hard a week ago. my head still hurts on one side with some swelling and tender to touch. should i go to the doctor?

You describe a localized area of bruising over the scalp. This should gradually resolve over several days. Medical attention would be needed if constant and worsening headache, dizziness and/or imbalance, nausea and vomiting, blurring or doubling of vision, and the onset of episodes of loss of consciousness. It is your choice whether to see your doctor at this point.