My brother in law had a shadow and after us all worrying it wasn't on the second x-ray which was only a fortnight later. From what he was told it can even simply be the position the lung was caught in during the scan as he hadn't even had an infection. I'd try not to worry. I think if it was likely to be anything more than inflammation they'd have put you on the two week referral path. I hope the symptoms that caused you to need an x-ray subside quickly. Lungs are really sensitive organs and post infection healing can take a while.

Wishing you health, 

L