Hello, thanks for using health care magic Since you took him to the doctor nothing was prescribed, it is likely that it is a viral infection. Viral infections are the most common causes of upper respiratory tract infection. However, they get super-infected with bacterial in most cases in which case, the mucus becomes yellowish and associated with fever. Give him much fluids to take in, keep him warmth and give protein rich food. If mucus is yellowish, then antibiotics will be needed. Best regards Dr Achuo