My 5 yo son is having cough from couple weeks. We are not giving any medication thinking it should go away normally. But it creates problem for him when he sleeps at night. His nose is also getting congested so he breathes from mouth and cough during night. Is ther over the counter medications which we can give him or need to see a doctor. He does not have runny nose and during day time the cough is not so frequent, only during night it increases. Thank you.