Breathing issue. Is it serious?

Hi my son was born on 20 may, 2023 at 32 weeks. He was on the ventilator for one day and CPAP for six days. Now he is more than one month old and the weight is 2.5 gm. Nowadays he is breathing with sound.it sounds like snoring sometime other times like a whistle..it mostly happens after or during feeding..I feed him through bottle as well as breastfeed. He also occasionally coughs and sneezes. Also while sometimes he flares his nostrils especially after feeding. I have observed retractions too around the collars bone area only and no where else.. oxygen saturation is Normal and there is no other issue..there is no blue coloration on the skin too. Most of the time the breathing is normal with no sound. Respiration rate is 30-40 per minute. I just want to know when and how the sounds will disappear. What medicines can I give this issue.is it serious?