Now, in order to stay true to the image, I'm going to do something I don't normally do. I am going to extrude some edges out but first, I merge a point of the chin area to a point of the fleshy part, making sure it stays quads (quads are important for smoothing in animation). So once those are merged, I extrude the edges as I mentioned before and then select two of these edges and extrude them toward the chin as shown. I will then merge these to the chin, creating whatever weird flesh thing is going on there that I drew....lord what was I thinking. Note that sometimes it's okay to deviate from your ref if it means keeping the anatomy realisitc.