It is possible to narrow the nasal sidewalls through a technique called osteotomies. Typically this does not cause any problems with breathing unless there is an underlying deviated nasal septum, which would need to be addressed at the same time.
Jason: The nasal sidewall can be narrowed in some noses. Please E-mail pictures of the base of your nose so I can determine if this can be done in your case. In response to your second question, the nasal wall narrowing should not be done if it will interfere with your breathing. I can answer that question after seeing your nose.
Yes, the nasal sidewalls can be narrowed to narrow the middle third of your nose. This needs to be done judiciously, however, as too much narrowing can cause difficulty in breathing. This area is the narrowest part of the nasal passage anatomically. Please consult with a board certified specialist who can best assist you.