I notice people tend to grow out of it or at least have it get milder as they age but of course your milage may vary. Try not to make any awkward scars. It is really embarrassing later. I always wear my fitbit partly to cover such a scar.
Your feelings are real. However you are not your feelings and while you cannot control everything that pops into your mind, remember that thinking is a behavior.
Having BPD is like having no skin and being required to live in a world that doesn't understand why you're so darn sensitive.