someone help!!

Hi ladies I just took my 2 month old Luis to the doctor cause he had a cough for a while they said they couldn't hear a infection he's heathy and well but the doctor said they could hear some cracking on his left lung I'm very worried she said she will call the peditrician then phone me back, anyone else had this? He's drinking fine apart from night time where he has a bit of reflux I'm so worried xx