Before you do anything insure that the device is completely powered down!
Go to the grocery store and buy the zip lock bags for the freezer that you can vacuum the air out(it works with water too). Place your iPhone or other electronic device inside and add rice too(it will capture the water as it is drawn out of the device). Now close the bag and start using the vacuum. Go back periodically and use the vacuum more. Two or three days later remove the device from the bag and gently warm the device(no more than 100 degrees). After a day of that you device should work. If not sell it to a repair shop and buy another one.