Good day, my son is 3 years and sick. he had rsv before throat infection and post nasal drip. currently i suspect the post nasal and throat infection again. he he coughing during the day but not to much. problem also worsen at night when he sleep?

Rhinosinusitis: Will cause postnasal drip throat irritation and worse at night. However would also need to think about the possibility of asthma which could also cause a recurring cough worse at night. Outside chance too of reflux as a cause. Best to get a doctor examination here to sort through these possibilities as if remains unclear will be able to order tests/refer to specialists