My sister had a big nose. Everyone says I will look like her when I grow up will I have te same nose

That's not necessarily true. If you and your sister have the same nose, that's purely genetic but since i am guessing the rest of your features are different, so you will not look like her. Infact when you grow up, you will look an older version of yourself- as you are right now :) Don't worry though. Puberty sometimes does wonderful things to people ;)