Leave your computer open for a day or so, preferably in a hot, but not humid, room so that it can dry out. Drying it out by hand doesn't remove every last drop of water that flowed in under a component or inside a connector.
After that, try starting it again. If the water was causing some short circuit but the protection circuits in the computer could handle it then you hopefully won't have any more problems.
If you're not so lucky, then you'll have to replace whatever you spilled water on.