OP- I have seen something similar. I had a rescue pass away from renal failure from eating too much junk. His testicles and cheeks swelled up SO big, the vet literally had to drain his testicles so they would not explode. It was horrific and so sad. We did all we could, but he died. So I know the HUGE testicle thing, and maybe something like that was going on with your chin? Any infection could do that also.
