Thanks for your question on Health Care Magic.
I can understand your son's situation and problem.
His Pulmonary contusions are definitely due to blunt chest trauma
because of fall.
But blunt chest trauma can not cause lung nodule.
In my opinion, this lung nodule is just a chance (accidental) finding.
At his age of 27 years, benign lung cyst
is the most likely cause for this nodule.
Lung malignancy is extremely unlikely.
Follow up with CT scan
of thorax after 6 months is advised.
This is to see for nodule activity. If nodule is of same size of decreasing than no need to worry, it is simple benign cyst
But if it is increasing in size than biopsy
So at present, no need to worry for this nodule. Get done repeat CT after 6 months.
Hope I have solved your query.
Wishing good health to your son. Thanks.