If a nose has been broken for over 20 years can it still be fixed?

Yes, you can fix a nose that was broken over 20 years ago. Obviously the technique is different than if you had gone in immediately after the injury, but it can still be done. The difference now is the nose will have to be "re-broken" before it can be reset, and by "re-broken" I mean controlled cuts in the bone in specific locations to move the bone in the desired direction. Also, if you have breathing difficulty this can be addressed at the same time. To get a full description of what you need, I recommend consulting with a board certified plastic surgeon or facial plastic surgeon with experience doing rhinoplasty and airway reconstruction.

The fragile nasal bones mend very quickly after the injury.  They are easily malleable for less than even a week after surgery, and by a few months are as strong as they'll ever be.  So unless you would have taken care of it immediately after surgery, there is no difference in having waited so long.  An excellent rhinoplasty surgeon would be able to fix your problem.  This is a commonly performed procedure, but it has to be done well.  So be sure to find someone very experienced with noses.

Old nasal fractures can still be fixed no matter how long it is been since the nose was fractured. See an experienced rhinoplasty surgeon for the best possible result.