I had this happen and it wasn't good. You can search for my thread "Death of a female panther" from 2008. Maybe someone who knows how to add the link can do it for me.
We think she got an infection from the mating and it developed over time and eventually killed her. A preventative course of antibiotics might have saved her, but who knows? I would definitely consult a vet, because it was a very sad outcome. I hope you have better luck than I did.