I would just ignore it. Put some sudocrem on the sore teat - this will help heal the teat and will taste sufficiently unpleasant that the kitten will go to a different one. If you really want to stop it, you could get the kitten a soft toy with suckable fur, which might distract it, especially if you rubbed it on the dog first so it picked up her smell.
We once had a cat which loved to suckle runt piglets in front of the AGA, We also had a siamese cat which started suckling from an older cat when we first got her. She continued the behaviour into adulthood, even once both queens had kittens at around the same time, so siamese suckled from older cat, while older cat's kittens joined in, and the siamese's kittens were suckling her. When the siamese disappeared for a few days, the older cat fed both lots of kittens.