A:Answer I have accidentally pierced screens in the past. It is a per set bases to be honest. If you do not notice anything instantly, chances are you won't a year from now. If you have protection on it (Geek squad or something else), you could always have it replaced if you are concerned that much about it. Generally you will notice discoloration within seconds of powering on. If you just pierced the back and not the panel itself, you should be fine. Perhaps attach a photo to help assist a little more?
Regards