What is probably happening is some water has found it way onto the PCB (the motherboard of the keyboard) and is bridging some connection, which is making the keyboard think you are typing multiple letters when pressing just one.
Worst case scenario, it could turn into oxidation, which is not good.. Best case scenario, letting it dry off more is going to fix it.
I am not sure what to suggest you, as I am not sure if the heat will only dry off the water, or if it can screw up some plastics too.
