There was another question that I answered about noses just a few minutes ago.
I will preface that with this hard to follow advice: You can let people get to you, or you can change the situation for the better. Now how you do this is up to you.
Personally, I'm dry heave ugly in general. but while it's a part of who I am, I do what I can to not let it define who I am. Sure, I'm a freak, but I've got the makings of one heck of a good husband. Now, once I can convince women to see past the appearance, I figure I'll finally have a chance at making me and my future family VERY happy.
I remember all to well my looks. I'm still shy around women, and it still hurts sometimes to get the treatment I get.
Middle and High school can be worse in many ways. In 6th grade, the idiotic teacher made us measure body parts. The nose was one of them, and my nose was the biggest in not just the whole class, but all of her classes combined. I hated doing that, and boy, I thought I was made fun of before. . .
So, my coping mechanism was to beat them to the punch-line. I'm funny (but looks aren't everything! Heyo!), and I'm an entertainer. Another way of coping, one that I'm trying to get rid of, is my extreme shyness and apprehension around girls. And anther one, was to be inspired to be a better person. There are things that are hard to change, and you have to live with those. Then there are things you CAN change. I chose to go for improving myself.
As for your sister; I think it's the job of a sibling to get under your skin and push your buttons. At age 28, I still poke fun and annoy my sister. She's extremely obese. And she loves purple, and she's short, so I always make references to the character of Violet from Willy Wonka. I also call her Shrimp, Dorkus Malorkis, Shorty Mcshortovich, dweebus. She calles me Dorkface. I ::cough cough lovemysisterverymuch cough cough:: So, you have to let it roll off. I call my buddies names, and while their insults, they're kind of like nicknames, almost like a brother. And they insult me.
I had a little 7 year old Japanese girl constantly telling me I was fat. I was 20 years old, 5'6 and 125 pounds at the time. I would always laugh and come up with a comment to annoy her, like she was my kid sister. And I would beat her to the punch by making fat jokes at myself. We all were aware I was super thin, but it was just a name she'd try to use because it was funny to think of such a skinny guy as fat.
Anyway, check out the answers here, and they might give you some insight.
link I wish you the best, and I hope you can take this to heart. or as I will say about me, I always take things to nose.