I wouldn't try a nail buffer. Since it's made of resin, you may just scratch the surface even more. I don't think there is anything you can do to prevent scratching inclusion pieces...other than not using them. Like Ammietwist said, if you bring it to a jeweler, you could ask if there's anything they can do to polish it...but then again, I doubt jewelers deal with plastic jewelry very often, so even they may not know what to do. (I'd personally just leave it. A piece of jewelry is meant to be worn. My D&G leather and crystal bracelet/watch is showing immense signs of wear and it was more expensive than the inclusion bracelet, but I still wear it almost every day)