Had a face and neck lift 16 months ago and now I have lumpiness under chin - advice? (photos)

Hello! I had a face/neck lift in September of 2020. All seemed fine at first until at about 6 months when strange things started happening beneath my chin. You can see the chin scar from the surgery and also, more towards my neck, another scar from a cyst removal, but in between there is all this lumpiness and cording (?). What do you think caused this and what can I do? It's really quite ugly. I have included a before picture if that helps. Thanks!