Keep a close eye on the bite. If it starts to look red and inflamed or if it is oozing liquid then you should take your kitty to the Vet. You can help by keeping the area clean and it is okay to put a little neosporin on the wound.
The first thing you should do is identify the frog and determine if it's a type that is venomous. If it is, consult a vet immediately. If not, just understand that your cat will probably be scared of frogs from now on.