Your best bet is to get a bowl of dry rice and cover your phone in the rice. then put the phone in a warm place for 3 days, Open your phone as much as you can e.g take battery out.
Try after that and if it still doesn't work then take your phone to a repairer and see if they can use some Isopropyl alcohol to clean up the board. If that wont work then Buy then get a cheap phone and use it untill the new Nokia 800 Lumia comes out.
Hope this helps