Final answer:
The nurse should ask the client to rate their pain level to determine their need for analgesia. Observing signs of restlessness and monitoring for facial grimacing are secondary assessments. Primary topic: pain assessment.
Step-by-step explanation:
The nurse should ask the client to rate their pain level in order to determine their need for analgesia. Pain is a subjective experience, and the client's self-report is the most reliable indicator of their pain level.
The options of observing the client for signs of restlessness, monitoring for facial grimacing, and watching for indications of decreased mobility are also important assessments to consider, as they can indicate pain. However, they are secondary to the client's self-report of pain.
By asking the client to rate their pain level, the nurse can gather the primary data needed to determine the client's need for analgesia.