Is it a large grinding noise that happens in intervals whenever the disc is usually spinning? The magnet that holds down the PS2 might have fallen out when it tumbled (that's what happened to mine, albeit in a completely different matter.) If you don't feel too uncomfortable taking apart your PS2, you can check. Before you do anything, however, allow me to find a few sites with instructions about taking apart one. There are a few things that are important about taking it apart (like not ripping the power strip off. That's a pain to reassemble.)
edit:
I need a bit more info. Do you have a regular PS2, or a PS2 slim?