It is nothing else than viral infection which is quite common among children. For this you can give the same medicines as your doctor had prescribed before or in my opinion you can give him syrup uthral 100 mg 5 ml once daily or syrup symbiotic-p 125 mg 5 ml three times daily with syrup wikoryl or syrup no-cold 1 tsf three times daily for common cold with syrup kofcef or syrup ambrodil 1 tsf twice daily. You can also use naso-clear nasal drops and salbutamol respules for nebulization as your doctor had already given. Don t worry much as any kind of viral infection will take 5-7 days to recover fully.