It is not recommended to administer medication intended for one person to another, as it can be dangerous. It is important to continue practicing good nasal hygiene and encourage your child to stay hydrated. If your child's symptoms persist for more than 7 days without improvement, or if their condition worsens, it is important to consult a doctor for proper diagnosis and treatment. Regular monitoring is important for now, especially if your child is eating, drinking, and having normal bowel movements.