Final answer:
The nurse should instruct the client to monitor and report persistent headache to the provider, as it could indicate an underlying health issue.
Step-by-step explanation:
The nurse should instruct the client to monitor and report persistent headache to the provider. Postpartum headache can be a sign of preeclampsia, a serious condition that can occur after childbirth. It is important for the client to seek medical attention if she experiences persistent headache, as it could indicate an underlying health issue.