Liquids in electronics cause 1 long term and 1 short term problems:
1) Electrical shorts: the minerals in the water (not the water itself) conduct electricity. This can allow electricity to "zap" something and fry the computer.
2) Corrosion: after the liquid dries it can leave behind residue. This residue can collect dust and other particles. Depending on the residue and other stuff, it can cause parts to corrode.
Number (1) is only a problem until whatever you spilled dries. That will depend on what you spilled and how much. But if it's been a while, then you probably don't have to worry about (1).
Number (2) is the long term problem. Whatever you spilled left something behind after it dried. Will that cause a problem? No way to know without taking it apart. Only then will you know what was left behind and where it was left.