Unfortunately foxes are starting to learn how to deal with hedgehogs.
It’s unlikely your hoglet will have survived this encounter, just from the bites alone. If you know where it was dropped you may get lucky and find it to get it help.
Small hoglets can actually be incredibly prickly but unless they can stay rolled up their bellies are just fur, and a foxes teeth are likely to have punctured them somewhere which will get infected if it’s not a mortal wound anyway.
It’s no longer a good idea to encourage both into your garden I’m afraid