Hi,
The shed process can cause them to make noises when breathing on occasion though. Does the noise seem to be coming from his nose or further down near the lungs?
Since he is in blue already I would probably wait until the shed is over then seeing if there are any signs of an RI after that.
More definate signs however such as open mouthed breathing or stargazing for extended periods of time or mucus in the waterbowl or smeared on the cage furniture means putting on a vet appointment rather than waiting.
dr del