My cat just fell 5 storeys onto a concrete floor, and his breathing has become labored. Should I be worried?

I can hear his chest fluttering when he breathes in. Could he have lung damage? We took him to a vet but he only gave him a shot, didnt x ray him or anything.. He is an overweight cat, 1.5 years old..

UPDATE:turned out his hind leg was broken. plastered it and hes breathing normally for now. maybe the pain was causing his shallow breath.