Have you ever met an expert? Someone who has special skill or knowledge in one field?
How about this: Have you ever met someone who thought he or she was an expert? Someone who believes to have a special skill or knowledge in one field?
My dad has been milking cows for 60 years; he is a dairy farming expert. For those 60 years, my dad has worn Rustler jeans and Dickies button-down blue shirts; he is not a fashion expert.