During a routine visit to the child health clinic the parent of a 3-year-old child reports, "my child is still sucking the thumb." what is the nurse's best response?

The nurse should not respond regarding the diagnosis of child's habit or the situation. However, the nurse should assist the patient while suggesting to see the doctor or physician first. The doctor itself is the person who should explain the diagnosis or findings to the parent of the patient.
In addition, there are some advises being followed in order to handle such a situation:

1. The thumb from the child's mouth should not be taken out while he or she is awake, it should be done after the child goes to sleep.
2. The parent’s attitude towards the child must be really humble and patient when talking about their child's thumb-sucking habit. They better not punish or shame him for thumb-sucking.
3. Last but not least, people in the surroundings must not be allowed to make fun of the child.