Hi.. Thanks for the query.. Well, nasal congestion can be due to a number of causes and the most common ones are sinus infection or sinusitis, cold, nasal polyps, allergies etc.. So first of all it is necessary to get him examined so that the exact cause f the nasal congestion is ruled out.. Treating the underlying cause will help in relieving congestion as nasal congestion is a symptom of any underlying disease and is not a disease itself.. Nasal decongestants can give temporary relief, however xylometazoline or oxymetazoline containing sprays can help.. Also elevate your head with chin downwards while sleeping so that the drainage is better.. Saline nasal irrigation can be helpful.. Use a humidifier in your room.. Hope this helps.. Regards..