Final answer:
The nurse's best response is to acknowledge the mother's concern and encourage her to share her observations, while also ensuring that the child's pain management will be adjusted if necessary.
Step-by-step explanation:
The nurse's best response in this situation is Option 3: "It's important for you to share your observations, and we'll adjust the pain management as needed." This response acknowledges the mother's concern and encourages her to communicate her observations. It also ensures that the child's pain management will be adjusted if necessary, prioritizing the child's comfort.