I hit my head on a cabinet yesterday and my head still hurts. Is this something I should be concerned about?

Not unusual. If the pain in your head goes away with Tylenol (acetaminophen) 1000 mg then you are probably fine. If you develop nausea and vomiting, imbalance, or have a headache that will not resolve with Tylenol (acetaminophen) then you should be evaluated.