Unfortunately, there's not a whole lot you can do. For starters, you should never turn on a laptop after water has spilled on it until it has completely dried out. Doing so may cause more damage. Depending on the conditions where your machine is drying out (humidity, temp, etc) you may need to let it sit for a few days. The components in there are very tightly packed and it can take some time for moisture to fully evaporate.
If you have let it fully dry out, about the only thing you can try is resetting the SMC:
http://support.apple.com/kb/ht3964
This can sometimes correct charging related issues. This will typically only help if the data in the SMC has become corrupt. There is a very slight chance this might have happened if your machine was powered on when the water entered it or if there was still moisture in there when you turned it back on. Unfortunately, the odds are against this... but there's no harm in trying.
There's not much else you can do apart from bringing it into Apple or an AASP to have them take a look at it.