Its really painful in the beginning, but it gets better over time. Not saying that it doesnt hurt, but you learn how to avoid getting punched in the nose. Easiest tip would be to tuck your chin. Also i never had a broken nose but my friend did and it looks exactly the same, it really depends on the severity of the fracture.
broke my nose twice during heavy sparring, needed surgery on the second one since my cheekbones were also damaged. after it got fixed my nose was still straight and no significant changes except a little hump in the middle of my nose. it doesnt look the smae bur its definitenly not significant, depends on how damaged your nose actually is though .
Im not fighting professionaly but i got it broken in a "street" fight. I was a little drunk so it didnt hurt but the day after you have the feeling of a pressure in your face which isnt really nice. also when you touch it its pretty wobbly and cracks a little