Is It Possible For an Xray of Nose to Show Prior Trauma?

It may be, but a CT scan would be more sensitive in finding old fractures so i suggest that.  Good luck!

Nasal bone x-ray are difficult  to interpret because the nasal bones are so small and have natural surture lines tha can mimic fracture lines. However, if the nose is twisted or has a step off fracture, that can be documented

Plain  x-rays of the nose are very unreliable in documenting old trauma. CT scans are sometimes better but in general the history of trauma and the physical exam is the most reliable. Your question implies that you are trying to get some documentation for your insurance to pay for your rhinoplasty. In Florida insurance companies take the position that surgery to correct an external deformity even if due to trauma is not covered unless there is a medical need to correct it (breathing problem?) It doesn't sound like your dorsal hump would qualify. Good luck!

If you break the bones of your nose they typically heal by what is called fibrous union.  Fibrous unions will be visible on an x-ray, typically for the rest of your life.  This is different from other bones which heal across a fracture with bone and eventually become impossible or nearly impossible to detect.

The value of this information is dubious however.  A nose that has had a previous fracture needs no treatment if it looks good and breathes well.  A nose that has never had a fracture, but looks bad or can't pass air well does need treatment.  Knowing that the bone has been broken really doesn't change the surgical plan, so I see no point in getting an x-ray.

If you injured the cartilage of your nose, this will not be visible on an x-ray. 

Yes an Xray of the nose will show nasal fractures but will not show evidence of cartilage tears or fractures and since cartilage makes up at least 50% of the nasal structure...an Xray doesn't reveal all nasal trauma.