You could try it as a summer squash but I doubt it will be very good or you could try keeping it, depeneding on how mature it is it may ripen in storage. I would keep an eye on it though.
Most pumpkins are not especially tasty, it depends on the variety but it may do OK grated in a bread or muffin recipe. It may even stir fry..I would doubt soup if it is really immature.
XX Jeannine