there is usually a manual override function. which is a small hole on the bezel, about the width of a paperclip. you can buy a tool to press it, but I find a straightened paperclip works well.
You just insert the tool/paperclip into the hole and GENTLY press until the drive pops open.
While this opens it okay, so you can get any discs out etc.... it sounds like your drive might be fried. Does it still play discs? and just not opening? or is it not working at all?