I'm thinking of changing my height since I'm someone who is socially awkward
Are you trying to improve your image?
Yes, I want to impress people.
Your height is something you can't really change. You don't have to be happy with it, but you do have to learn to accept it.  Just try to be more confident when you meet people.
I'm going to hurt myself and then change my height.
I'll admit that there are small things you can do to change your height, or at least, perceived height: high-heeled shoes, or shorter hemlines can certainly make your legs look longer, so you could try those.  However, you mentioned that you want to hurt yourself, and I have to advise you not to do that.  Hurting yourself won't help anything, so you should talk to someone if you ever feel that urge.