This is education, not advice
The information here is written for the general reader and does not replace a personal medical consultation. It cannot tell you which layer is producing the width in your own face, how thick your mandible is, or whether an operation is appropriate for your health or your circumstances.
Removing bone is easier than restoring it
Bone that has been removed cannot be put back as it was, and material used to rebuild a contour does not behave like the bone that was taken away. Over-reduction is therefore the error this operation most wants to avoid, and nothing on this site should be read as suggesting that a more aggressive reduction is a better result.
No outcome is guaranteed
No treatment can be guaranteed. How the swelling resolves, how much of the planned change reads through the soft tissue, how sensation returns and how the two sides settle vary between individuals, and the result is judged honestly at around a year rather than in the first weeks.
Numbness and nerve weakness
Numbness of the chin and lower lip is expected after this operation and is watched over months; some areas may not return fully. A weakness of the lower lip from the marginal mandibular nerve is usually temporary and usually resolves, and a lasting weakness is uncommon but possible.