By son got cold on 12th of may. After that cold get better.cough stuck in chest as whenever he cough it sounds like that. He is fine. But whenever we use Ac in the night. Morning he feel little bit runny nose very little. whenever he coughs it sounds khad khad like sound. Very light cough but sounds he has problem inside and not going completly. What we can give him for complete relieve. We have not given him nebuliser since he born to  till now can we give now?? It will work?