If you believe your 2 and a half-year-old child has a cold sore, it is best to take photos of the lesion and show them to a doctor during a future appointment for a clear diagnosis. If the lesion is not too large, there is no need to worry at the moment or consult immediately. However, if the skin is very damaged and the lip becomes very swollen, it is advisable to seek medical advice. It is important to try to prevent the child from touching it, as cold sores can spread to other areas of the mouth or near the eyes.