The photo of the tiny blackened toe just reminded me of the day old chick I had long ago that had a toe injury that I noticed after bringing the new chicks home from the feed store. Despite all my first aid attempts, it shriveled and fell off. The injury at first was very painful for her, but after it blackened, she seemed not to be bothered by it, and missing a toe never caused any further problems for her.
I had one other older chicken lose a toe like this. When it got to the stage where it was detaching from the foot, hanging by a thread of tissue, I just cut it off, and she was just fine from then on.