You chin procedure is called an advancement genioplasty. This is done by advancing the lower border of the mandible(lower jaw) and pogonion(chin), which has no affect on the teeth or your bite. As a result, this procedure can be done before or after braces. I would suggest seeing an orthodontist for evaluation.
I will tell you from experience that most of the time the chin is setback in relation to the upper jaw, the problem is the positioning of the lower jaw bone. This would require a bilateral sagittal split osteotomy (lower jaw advancement) to correct your chin position. If your chin point is also recessed, then the chin can also be done in combination with the lower jaw advancement. Advancing the chin where the underlying problem is really the lower jaw can have negative esthetic affects on your profile. Also, I would highly recommend seeing an oral maxillo-facial surgeon for evaluation. If you only need a chin advancement they will advance your bone rather than an implant which maybe used by a plastic surgeon. Your result will be much more pleasing and natural.
I have given you some big words which you can google to do you own research.
