Final answer:
The nurse's next priority action is to reassess the patient's pain level in 30 minutes.
Step-by-step explanation:
The nurse's next priority action for this patient would be to reassess the patient's pain level in 30 minutes (option c).
After administering acetaminophen for headache relief, it is important for the nurse to evaluate the effectiveness of the medication and determine if the patient's pain has been relieved. By reassessing the patient's pain level, the nurse can gauge whether additional interventions or a change in the plan of care is necessary.