What if I tell my sister her boyfriend can't come to my wedding?
Why do you not want your sister's boyfriend at your wedding?
I'd rather have a dog or a goat at my wedding than a guy with a big nose
That is an odd reason you give but regardless it is expected to have a few unwelcome guests at your wedding. It is best you try to be a gracious host.
I don't care if society agrees. This is about what I want.
Honestly, while this is your wedding and you can do what you want, your sister is going to be very upset by this request and it sounds somewhat like a cruel one. Do you want to be known as the cruel person who refused to let someone into his wedding for having a large nose?