Cut it off. If it is a little tough you can soften it by a hose, or baby oil and then just twist it off. I can't stand it when the chesnuts get long. I am forever peeling the ones off my horses when I pick their feet.

I have a client who has a dog that everytime she is around the horses, the first thing she does is walks up to one of them and starts nibbling the chestnuts off. The horses don't mind one bit. It is the funniest thing that I have ever seen.

But anyways it should be fine to cutt it off (use you new knife )and as long as there is no open wound you shouldn't need any antiseptic.