My lower jaw and chin seem underdeveloped - how can I correct lower jaw? (photos)

I would look into having a genioplasty. This is a permanent procedure that would add length to the bottom of your face, creating more facial balance. You already have a strong jawline but your chin is a little short. A genioplasty would also improve the labiomental fold, decreasing the shadowing you have under your lips.

You have a shallow midface combined with facial aging changes and elements of mandibular deficiency.
Avoid buccal fat removal since an aging face needs fat for contour. Consider cheekbone augmentation and a genioplasty for the simplest approach