As you description,i also advise to consult your family doctor for a clinical examination if you have severe headache and undergo CT scan.
Possible differential diagnosis may include Concussion.Chances of head injury are less however possible.
Serious brain injury would generally make itself known over the first 24 hours, even over the first 6 hours.
Serious bleeding which would cause problems would certainly have caused symptoms (worsening headache, dizziness, lethargy, confusion, vomiting, numbness, weakness, etc) within hours.
It is common after bumping the head against something to experience some headache (most likely due to the jarring effect), and this should gradually get better and resolve completely.
Take OTC Tylenol only for headache.
If you have associated vomiting,dizziness,blurred vision,disorientation then you should visit ER for prompt management.
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