What Causes Continuous Nasal Congestion?

It sounds like sinus infection but you would have to see a doctor to be sure since I am not a doctor...my sister and nephew have had this and had to have a minor surgery to correct it,and it could also be polyps in the sinus cavity...so again see a doctor before jumping to conclusion since I am not a doctor...

Lack of water, infection, cold, sinus infection, overproductive glands, genetics, etc...