My puppy hurt leg, won't eat/drink, can't walk. What's wrong?

Thanks for using Petco Pet Education Center, formerly Petcoach! Poor Hallie! She is possibly not eating due to pain associated with the injury which often times can affect a dog's appetite. Of course other unrelated causes for her not to eat cannot be completely excluded. With these types of injuries, there is usually more trauma than what can be seen from the outside. I recommend that you have Hallie evaluated by your veterinarian for further assessment and treatment. They may take radiographs to check her bones in the affected leg. They would be able to check the extent of her injuries and proceed with therapy as indicated. She may require antibiotics, further local wound therapy and pain control medications. Good luck and best wishes!