Does it show an icon for the CD on your desktop? You should be able to right
click on the icon and either unmount or eject, or maybe even both.

Does the CD get mounted or is it in a state of being in the drive but not
mounted onto the filesystem?

You can check this in the Terminal

2 steps:
1) issue the command "mount" (sudo not needed) with no options, just type the
word mount and hit ENTER. You will see a list of drives and other things
the filesystem has mounted.

2) If you know your CD/DVD is in the tray and there's no app currently using
it, just enter the command "eject" and press ENTER

It should then eject unless there's a "resource in use" type of error.