How to Remove a Stone From a Tap

We let him take them into the bath with him to play with. While we weren't looking, I heard a little wind. Mummy, mummy, gone, gone. What's wrong, Jacob? What's gone? Stone, gone, stone, gone. Well, it can't be very far. He'd shoved it into the tap and it was lodged. It still is lodged. We were never able to remove this stone from our tap. Now trying to get a full flow of water out of this tap is just impossible. So we have a dribble of water that comes out when we turn on our lovely tap. It's very frustrating. Not the only frustrating thing, actually