TouchID sensor isn't that easy to fool with replicated fingerprints.
If you are afraid that some one will cut off your finger to unlock your computer don't use the touchID, that said if some one is willing to do that to unlock it i wouldn't want to imagine what they'll do to you to get the password.
Starbug (same guy who was the first to fool a Touch ID sensor) demonstrated that he could create fingerprint masks from press photos of a politician. See his very entertaining talk at 31c3: http://youtube.com/watch?v=VVxL9ymiyAU
If you are afraid that some one will cut off your finger to unlock your computer don't use the touchID, that said if some one is willing to do that to unlock it i wouldn't want to imagine what they'll do to you to get the password.
;)