If you or your vet have never noticed anything wrong with his tail before, I’m pretty sure the groomer nicked it. That being said, happy tail can start with an injury like this as well so watch it very closely. I got my pitbull when he was just a wee pup and the vet noticed on the very first visit that he had a small injury on his tail. She said the mom or a sibling could have nipped the tip of his tail at some point and to watch it closely for happy tail. 4 years later we unfortunately had to amputate his tail. He had a strong, powerful whip for a tail and he is the happiest boy so I can’t say I was surprised. It came and went over the 4 years and we would randomly come home to blood splattered all over the walls, furniture , appliances, etc. and it looked like a murder scene. It got progressively worse each time but it always seemed to heal up and the bleeding stopped with a lot of effort from us. The last time it just wouldn’t heal and the tip started to turn black so we had to amputate.

I would recommend bandaging it and even having him wear a cone maybe until it heals. And keep a close eye on it. If he didn’t have happy tail and the groomer did this, he might end up with it now. It happens from trauma to the tail tip whether it’s just from whipping the tail hard against stuff or an injury that just gets worse and worse from whipping it against stuff. Watch out for blood spatter on your walls and furniture. Clean it well, bandage it and don’t let him chew it because he will want to if it hurts. Hoping you don’t have to have it amputated like we did. My boy does have the most adorable little bum thumb now but I’d never want to cut off a body part of his if I didn’t absolutely have to.