Thanks for your query
your son is having respiratory infection.
continue with medication suggested by your pediatrician
Regarding apprehension in not using nebuliser i would like to clarify that giving medicine through nebuliser is totally safe,it is just a mode of delivery of medicine.with nebulisation medicine goes directly into lungs,dose required is less than other routes,effect is early with less side effects.
do regular follow up with your doctor
Your son will be fine.