My bunny is limping, and I don't know what's wrong?

Yesterday my boyfriend bought me a bunny because earlier during the week I had mentioned if I were to get a pet, I'd want a bunny. Now it's a nice gesture don't get me wrong, but I don't know the first thing about taking care of an animal. I just noticed that my bunny isn't putting any weight on her left leg. I have no idea what's wrong; I have an appointment at the vet on Monday, but I don't know if something is wrong, and I may need to take her now. Does a limp mean that something is seriously wrong?