Dryers take 4 inch ducting. Ceiling fans take 3 or 4 inch ducting. Your dryer will still work, but the reducer will add a lot of resistance to air flow, and so your dryer will take a bit longer and a bit more electricity to dry your clothes.
Is it not possible to enlarge the hole and run 4 inch dryer vent pipe?
When installing vent piping, the shorter and straighter the vent pipe, the better. Use straight rigid galvanized or aluminum vent piping instead of the vinyl ducting or flexible metal ducting. Also, hold your joints together with duct tape only. Never ever never hold dryer vent connections with screws like they do on flue ducts. Lint can collect on those screws and create a fire hazard.