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It could be a normal variation / or from previous infection.
Nothing need be done.
Interstitial disease and collapse present a totally different picture.
No one treats an X-ray! It is the patient as a whole, to be assesses.
You have not stated your age, gender, personal habits, family history or co-morbidities
If you are doubtful, consult a Pulmonologist
/ go for CT chest and Lung Function tests / more to reassure you, than for the child!
Wishing speedy recovery