You can't. And as you've found out, but for the benefit of anyone else who may be reading NEVER INSERT A NON-STANDARD SIZE CD/DVD INTO A SLOT LOADING CD/DVD DRIVE. They WILL get stuck, and the ONLY way to get them out is to take the drive apart. Also, these discs may end up shattering inside the drive destroying it and the drive.
You will have to take this to a repair shop, and they will have to take the drive apart to get the disc out. I had to do this recently for an iMac, and it shouldn't take them too long to do it. There is a chance that the drive will have to be replaced, and this will be considered accidental damage and not covered by the warranty. Just so you're prepared for what might end up being a rather expensive repair.
My wife inserted a small disk into the cd/dvd slot and it will not eject. How do I get it out, short of taking it to a repair shop? It is a MacBook 3.1 Intel Core 2 Duo running OS x 10.6.3