Oh dear!!
Well when i was younger i dropped my tamagotchi in the toilet (dont ask! ).
What i did was, took as much of it apart as possible, eg battery out, back off...
Then i put it on some really absorbant tissue paper then put in the airing cuboard for a couple of days, and hey presto when i put it back together it worked!
I think the sooner you do it the better.
Good luck!