In the event that a disk has become stuck in your Macintosh computer, there are several steps you can take to try to force it to eject.

1. Restart your computer, and hold down the mouse button. If you have a 2 button mouse, hold down the left click.
2. If your computer has an eject key on the keyboard, restart the computer again, this time holding the eject key.
3. Open a Terminal window and type in drutil tray eject.

If neither of the above work to eject the CD, MacRumors has additional information on how to Force Eject a Stuck CD or DVD.