By removing excessive amounts of fat in the chin and neck region, it exposed your platysma muscle. When the platysma muscle contracts it can form bands. These are called platysmal bands, and tend to be more prominent with age. It’s uncertain if you’re extending your neck, but doing so will probably activate contraction of the platysma muscle. I’ve also seen people develop firm cord like scar tissue structures that slowly improve over 6 to 12 months. It looks like your surgeon was a little heavy handed with fat removal. Liposuction is a permanent and irreversible procedure. Sometimes fat can be brought back in the area with fat grafting but the procedure is technically difficult when done to correct overly aggressive Liposuction. There is no easy fix for what you have. Regular platysmal bands are sometimes treated with Botox but that’s a little different than when the entire platysma muscle is exposed from overly aggressive liposuction. No straightforward, easy solution. Best, Mats Hagstrom, MD