I've found a couple similar. They more round and uniform.
They came from a very early pottery site.
Where did you find it?
I have been told there were possibly used as stoppers to cover the mouth of pottery vessels or as heating stones.
I've also wondered if they could be for a game.
These are clay cooking balls that have been fired like pots are done. Notice the smoothness to the outside of them, you would not wont something that was flaking or falling apart in your food.
Mother nature can be a great trickster.