This is an important question and it is a topic that must be considered for major revision rhinoplasty. Most revision rhinoplasties require that additional structure be added to the nose in order to achieve a stable nasal framework and adequate airway.
The risks to using rib cartilage for revision rhinoplasty (also know as a rib graft) are very small, but in your conversation with the physician prior to surgery, I think it is important that several topics be covered.
1) First the donor site in the rib is often more uncomfortable after surgery than the rhinoplasty. Exercise is restricted for several weeks after surgery. There is a very remote possibility of having a collapsed lung which would be recognized in the operating room and treated (I have never seen this occur). A visible scar is a potential, although we try to place incisions in locations that are not frequently seen.
2) A graft by definition is tissue taken from one area of the body and placed into another, which would require a new blood supply in the recipient field. Occasionally this does not occur, and with that a graft may re-absorb over time. In healthy patients, this is a very rare occurrence.
3) Grafts can occasionally warp and will require a revision procedure. However, on balance the value of a rib graft well-outweighs the potential risks, and it is an important option the surgeon must have at his disposal when carrying out a revision rhinoplasty