Steroids (omnacortil) and antibiotics are usually not required in such viral illnesses, consult a  pediatrician for better treatment and get your child vaccinated with influenza vaccine after illness subsides.

You don’t give any previous history of cough and cold with chest congestion - how frequently he had those symptoms- in acute attack- may need oral steroid- that should be started within 48 hrs to get result- repeated attacks inhalation bronchodilator +_ inhalation steroid and Motelucast according to frequency of attacks and you should consult for influenza vaccination-

Consult with Pediatrician physically for further evaluation and treatment