It may be you have a piece of the shattered cd still inside the player,and this is causing it to keep opening.
Take the cd player out of the pc and have a look with the cd drawer open see if you can see/hear anything moving around.
If you are able you may be able to take off the covering from the player and get a better look,but doing this may well invalidate any warrenty on the player so i will leave that choice upto you.
You could have damaged the drive mechanism as well
so it may be cheaper to get a new player.