Is it possible that something is somehow stuck in the drive preventing it from opening?
In any case, there will be a small, circular hole on the front of the drive. Get a paperclip or something similar and push it into the hole. This will release the drive tray slightly, and you can pull it out with minimal force. Make sure nothing is stuck in the drive, and then try using it again with the button.
P.S. Best to do this while the computer is turned off.