It is glass so there's always a chance of scratches. If you're talking straight nail, no extension, false nail or gem implants, it's highly unlikely. Having said I've had gorilla glass scratch with a coin, which shouldn't be possible.
I guess I have to ask, does your camera lens have a scratch? What makes you believe it's from your nail?
It would be far more likely that it was scratched by something else and went unnoticed until you felt it or noticed it than something like a nail would cause a scratch.