Having cough in day time. Lungs clear.

My son is 3.9 yrs old, and from one week he has cough in day time.may be around 7-10 times  in day..we visited doctor 3 weeks back that time he had cough a lot..and especially in night sleeping time.he got up in the night and cough badly..docotr checked and told lungs clear.its a dry cough and will go.he didn't recommend any medicine but asthalin nebulization 3 times a day and budecort 2 times a day for first 14 days.after 2 days follow up when we said doctor still cough in night he mentioned omnicortel forte 4ml 2 times a day..after 4 days s oral medicine improved but now although he improved in night but more mild symptoms of cough in day time..seems like dry cough.. 2 months back he had right upper lobe pneumonia and admitted for treatment..for 5 days.as he had cough and fever spikes.he had bronchoscopy as he had mucus plug in airline of lung..after removal he got fine and again started cough in 1 month only..plan. guide for medication..or shall we continue budecort in night once