He is likely fine. Just keep an eye for anything strange or more sneezing fits. My first rabbit didn't like a cleaner I used, so I had to change it. She also caught what I call the Chinese cold once. My husband came home from a business trip there, sicker than a dog with the worst cold ever. She got sick with sneezing soon after. Doc said it was a cold. Weird. Now we stay away from the pets when sick
My first rabbit would sneeze if she drank too fast. This one will sneeze after cleaning himself.