Final answer:
The nurse should document the allergy and withhold the medication to ensure the patient's safety.
Step-by-step explanation:
The nurse should take the following action first: B) Document the allergy and withhold the medication. It is important to document the patient's allergy and withhold the medication to prevent any potential allergic reaction. Administering the medication as prescribed could have serious consequences for the patient. Before proceeding with any action, it is crucial for the nurse to prioritize the patient's safety and well-being.