Room Escape Puzzle

You awake to find that you are in a strange room. The room has only one door and that is locked. The floor, walls and ceiling of the room are completely white. There is no furniture in the room apart from a large white box with a small hole in its side.

You try to open the box and its lid opens to reveal that it contains nothing except a piece of paper and a key.

Written on the piece of paper are the words, “A major clue”.

You take the key out of the box and try to unlock the door of the room with it but discover that there is no keyhole in the door and not even a door handle but you do notice a sign upon the door which reads, “You need a different kind of key to open this door”.