I need advice really bad please!

I always hide my hands in my sleeves because they are always cut and and my nails are very short! ds :( I just say. Well my friend keeps asking to see my hands. But what should i say? no one except mom knows about this but she does not care. :( Also, i have been trying so hard to stop but it has not lasted too long. I was wondering what things i could try to stop doing it? I will try a stress ball and squeeze it when i feel the urge to pick. What should i tell people that ask why i am carrying around a stress ball? I will not tell them the truth! its too embarrassing. Also prom is coming up and my nails are really and hands are really bad. What can i do to help them look better and not pick until then? Thanks :)