Whoa whoa whoa whoa whoa, gonna have to stop you there.
To preface, I don't really know you. I don't know if you've been lying about your age, or any of the things you said, or etc but regardless of whether or not your words hold any water, I can't not throw my two cents in on this.
Assuming you aren't lying, don't do that. Speaking from firsthand experience it doesn't help, and the guilt and paranoia that accompany doing so aren't worth it. You also risk getting an unnecessary infection. Even if they're not visible, living with the scars isn't exactly fun either. Just don't do it. There's healthier coping methods out there like talking to someone, exercising, napping, writing things down, spontaneous showers, holding ice cubes, drawing on yourself, and etc etc.
Assuming you're joking or not being serious or whatever, don't do that either. You don't know who will hear you. Though the term's been bastardized by tumblr, you could actually trigger someone by bringing such a thing up. You also might be heard by someone like myself or by someone who, rightfully so, takes things said like that seriously.
Or if you meant that in the third way that just occurred to me, ignore what I just said and be more careful when holding sharp objects.