Is there a morning after pill for dogs? If so is it an injection? Please help

Yes, there is a mis-mate injection, but you only have a 24 hour window to get the shot. Hurry to your vet ASAP! You should really put heavy thought into spaying your dog. If she tied up with a male, it will prolong her heat cycle, and its just likely to happen again, and obviously you are not looking to have puppies. Spaying her will overall help with her health and quality of life. A spayed female has a lower chance of developing cancer.