Get evaluated. . There are many causes for nasal collapse such as trauma, congenital, and post surgical. You should be evaluated by a experienced rhinoplasty surgeon. There is nothing that you can do except protecting your nose from injury.
Support is key. The collapse is due to lack of support caused by problems with the cartilage or excessive scar overpowering the cartilage. Options include external support (breathe right nasal strips) or internal splints (available commercially in a variety of forms) or via surgical support with cartilage grafts.