as far as i know you do not use o rings with the nozzle. none of my airbrushes do (iwata hpc plus, doesnt. my badger is a push fit. my cheap 'n cheerful one doesnt either.
of course your could be different. but....i cant find anything on yours to confirm it.
there are o rings further back in the airbrush, but these are to seal the needle not the nozzle.