Just let them know before and after the appointment that they might be sore (they are going through a surgery) and for most people, some OTC painkillers will be sufficient if needed at all, BUT if they need to, they can call you and you will prescribe a stronger painkiller for them. Or, if you cut them bad, and if you trust them (probably more a possibility in private practice then at school) just send them home with a prescription telling them if need to get it filled, but if not, just shred the prescription.