i agree with dawn. URIs can move fast. pay close attention to him and make note of any other changes.
my chin had a URI about a month ago. it started with a few small sneezes and i eventually saw little crusties around his nose. took him to the vet on a friday and received 2 antibiotics for him. on saturday, even after taking about 2 rounds of his meds, he was sneezing a lot.
especially if there are a few sneezes one right after the other, its not just an irritant like dust bath or shavings. get your little one to a vet. listen close to his breathing to hear if its labored or making any other sounds. some people describe it as a "clicking" noise. i just heard a few squeaks every so often. discharge around the eyes is another symptom. regardless, if the sneezes are periodic, i would suggest a vet visit. you dont want to wait to see if other symptoms appear. my chin was prescribed Baytril and TMS (trimetha sulphide?- something like that).
good luck and keep us updated. if its a URI, hopefully you caught it early!