I read your question carefully and I understand your concern. The kind of trauma you describe generally would seem not dangerous, not enough to cause any brain injuries. Even if there was such injury usually bleeding or swelling in the brain causes raised pressure in the skull, while that type of headache you describe on standing up is typical for low intracranial pressure. So it is hard to make a direct relationship between the injury and the headache. However since it is a recent onset headache with features of low intracranial pressure it must be investigated. Blood pressure measurements supine and sitting are necessary to check for drop of blood pressure. Brain imaging with preferably MRI is necessary to look for causes of low intracranial pressure and if the findings are still suggestive of that a lumbar puncture as well. In the meanwhile usual analgesics like paracetamol and drinking plenty of fluids are recommended. I hope to have been of help.