Hope Chewbacca continues to improve quickly. Since that looks like a hematoma, be aware that as it resolves and resorbs, it may get to looking worse before it looks better.
Gravity always wins, so that blood that is now contained will spread out as the scrotum flattens back out and Chewy will probably end up with bruising down his inner back legs. This will not indicate any new bleeding ir injury, just that blood spreading out. I would just watch for any signs of increased pain, heat or drainage at the area and get him rechecked quickly if any of those occur.
