first turn it off and remove the battery if possible.
get a can of air and try to blow out all the openings on the phone. including the microphone.
typically newer phones are pretty water resistant and you might just have water in there blocking sound.
if that doesnt work while its still taken apart put it on a vent for like your heating and leave it for a day or two to dry out further. DONT NOT PUT IT IN RICE lol! the debris from the rice can get into places you dont want it.