I am really sorry you felt you had to do that Mike. I hope you are taking care of your hand.
It can be really, really difficult to get rid of that favourite tool. It's one of the biggest steps you can take in symbolizing your commitment to stop harming yourself. I like ickydog's suggestion of giving the tool to a friend to get rid of it, when you're ready, if you can't get rid of it yourself. One thing you could try as a first step? Put it somewhere really inconvenient. Like behind a beam in the attic, under the spare tire in your car, outside tied to a tree, under boxes in the basement, etc. This way it takes a few minutes to retrieve it, and gives yourself some time to stop and think about whether cutting is really what you want to do right then.
Thank you for sharing, I hope you'll continue to feel better.