Prominent vascular markings means either Infection or Inflammation in respiratory passages, Allergy
or fluid overload.
But diagnosis is not made only on the basis of X ray
It should be co related with symptoms & signs obtained by physical examination.
So, it will be better to consult a Pulmonologist
Appropriate management steps will be taken based on complete history, physical examination & co-relating the findings with investigation reports.
And make sure that your son is adequately breast fed & well protected from cold
, dust & other allergens.
Wish him a good health & speedy recovery.
Thanks & take care.