As a general rule, if a device doesn't come with a stylus, you probably shouldn't use one with it. If a device does come with a stylus, you should use only the stylus it came with, or replacement styli from the same maker. Otherwise, you are opening yourself up for trouble.
There are exceptions of course (Wacoms and the various styli designed for use with them).
I'm not sure how much difference there is between the plastic used for touch screens used for tablets like the Nook HD+ and the plastic used for optical media like CDs and DVDs. Sometimes a scratch on the bottom of optical media interferes with playback and can be remedied with kits sold at some music and video retailers. The kit I purchased includes cream to apply to the disk (with a foam swab) and a soft cloth for wiping the cream off. I believe at least some of the benefit is the result of some of the cream filling the scratches, the cloth removing the dried cream from the flat areas beside the scratches. I'm not sure if similar kits would be safe or effective on a scratched tablet screen.