It's normal to weep when your nose gets hit.
Tears are on-going secretions of lacrimal glands which lie in the bone concave above orbit.The secretions keep the humidness of eyeballs and most of them will evaporate into the air ,and the remains flow into nasal cavity through two lacrimal ductules located in inside canthus,so you don't feel the secretions.
But your lacrimal glands will be irritated too when your nose gets hit,and then you weep.
It is a natural reaction of human body. You know, tears sometimes are sign of your emotion when you feel happy, sad and pain etc. When you hit the nose, you must feel very pain on your nose, making you got watering eyes. That is just tears not really water eyes. As long as you release yourself from such pain, your eyes will stop water. So, what you need do is to take care of your nose. If your nose hurt, you'd better use some medicine to treat it.
It is natural. First nose pain is followed watery eyes. Well, there is a nasal passage between nose and eyes, through which tears flow down. But when nose gets hit, some other fluid might block the path, so the tear can only flow out through eyes.
Have you ever had that experience, when you apply eye drops, it might flow out your nose or even in your mouth. Because eyes, nose and mouth are connected by a common path, nasal passage.