Final answer:
The nurse should complete checking the patient's heart rate before administering the medication.
Step-by-step explanation:
Prior to administering the medication, the nurse should complete checking the patient's heart rate. Since Corgard (nadolol) is a beta blocker, it works by blocking beta-1 receptors, thereby slowing down the heart rate. Therefore, it is important for the nurse to assess the patient's heart rate before giving the medication to ensure it is within a safe range.