Prominent chin when smiling? What can be done? (Photo)

Both answers below are correct. The dimpling that occurs is when the chin muscle "mentalis" flexes. Botox here by an experienced provider (or else it can affect your smile) helps dramatically. To the extent that in the first picture the chin hangs a bit lower than the jawline that would need surgical correction. Try the botox first, can make a tremendous difference and you may very well be happy with that alone.
I hope that helps!

Jeffrey Watson, M.D.
Facial Plastic and Reconstructive Surgeon
Graduate, Harvard Medical School

You have excess soft tissue of the chin that sags off of the bone. This can only really be improved by a chin ptosis correction procedure done through a submental approach with removal of some of the soft tissue with tightening.

The droop you see is from contraction of the chin muscle. Without getting extravagant about  disassembling your  chin I would simply try some Dysport or botox in the chin muscle.  I would expect some improvement