Make sure it isn't broke. I have a dog with a kinked tail and it doesn't effect her running or anything of that sort. Also have a dog with a broken tail 2 inches from the tip have been to the vets, vet said to leave it alone and make sure it has the blood flowing through. Also check the skin colour of the pups tail and make sure it is pink in colour so the blood is pumping through to make sure it isnt broken.