Click on Finder in the menubar and select Preferences. Make sure there is a tick at:
Show these items on the desktop:
"CDs, DVDs, and iPods
See it that shows the disc icon on the screen. If so, then just drag the icon to the trash to eject it.
If that doesn't help:
Try restarting and holding down the eject key during startup ... keep it held down and see what happens.
Another method is to launch iTunes and in the menubar select Controls and down the bottom of the pull-down menu is "Eject Disc". Try that.
Have you tried Disc Utility? Any disc in the drive should show up in the left collumn. Click to highlight it and select Eject .... BTW Disc Utility is found in Applications ~> Utilities ~>
Finally there's a Terminal command you can try:
Launch the Terminal and type following command: