Ejecting a disc on a Macbook? HELP!?

So, when purchasing an album on iTunes, a message popped up that said I should back up my iTunes library. I pressed okay, went through the options, then it told me to insert a blank disc. I did. after a few minutes it had an error, it couldn't add my music to the disc. I pressed retry, and then it said that the disc in my computer wasn't a blank disc. I closed out of iTunes, and on my screen the disc wasn't there as an icon. I went back to iTunes and pressed eject disc, command + E, and I pressed it from the menu. The disc is still in my computer and I have no idea how to get it out! Any help?