If a 14-month-old baby has a cold sore, it is important to make sure it is not impetigo. If the issue is localized to a lip blister and there are no other symptoms present, a doctor's visit may not be necessary. There is no specific treatment for cold sores, but you can help alleviate discomfort by using a moisturizing cream and giving acetaminophen if the child appears to be in pain. Keep an eye out for any new symptoms inside the mouth or changes in temperature.