We need more info., please.....I'd say a vaccine reaction or nerve pain from the injection......The Distemper vaccine seems to be notoriously dangerous, especially for small guys.....
If this is a dog that gets vaccinated yearly, then that ups the chances of a serious vaccine reaction....How old is he....
Get your guy back to his Vet today!!! Please, let us know what happened...Thank you, Karla
Was it just Distemper or a combo and how old is the dog? Since I am just seeing this, I hope your dog is doing better. If not, and especially since it is a small breed, I would be contacting the Vet uf symptoms get worse. Good luck and please update.