I would advise you to follow the "rules" you mention. If you have a headache then take what was recommended which I imagine was Tylenol.The waiting is necessary and you need to calm yourself and not get so stressed about this biopsy. If you feel that you need some type of medication for your stress level then I suggest that you contact your Primary Care Physician and ask for something. Regards ....
It would be best to check with the surgeon who set up the "rules" for you. S/he is the only one who can answer that question for you.