Suggest Remedy For Constant Cough Due To Sinus Problem

Dear Dr. my son is 11 year old, and he is suffering from coughing since last 4 months, he was admitted in hospital in october 2013 and slowly he cured but since last week he is coughing non stop again, yesterday i had shown him to chest specialist, he asked for x ray, and report is he has sinus in left side, kindly advise me