Hi and welcome to HCM.
first,this can be nothing usually due to eblarged pulmonary vessels or lymoh nodes. Secondly it can be sign of mild acute pneumonia
and you dont need to have any symotoms of it and third it can be sign of chronic brochisit,asthma
or any other chronic pulmonary disease especailly if you are a smoker and live in pollution air area. It shouldnt bother you for preemployment tests. After the follow up you ll know is there any progression or this was nothing. WIsh you good health.