We processed our young dual purpose birds yesterday at about 12 weeks. This one was a hen, but we culled her because she was constantly being pecked in the head by our meat chickens, then our layers when we moved her. After processing, my husband saw what looked like a very small hole on her leg filled with cornmeal. After cutting in a little more, then a little more, this is what we found. It was in the meat, not between the skin and meat. Any idea what this is? It also had a very strange odor, similar to when someone flosses their teeth after not doing so a long time, that gross bacteria smell. (Weird way to describe it, but very accurate). It was firm, almost rubbery in texture. Again, this was on the leg, not anywhere near the organs or whatever. Needless to say, we aren't eating this one. You can see part of the "cornmeal" texture on the third pic.
Well I think you know it's an infection of some sort. Abscess? Ew!! Unfortunately I have nothing to offer but "ew"!!!
I have come across that at times, probably comes from an injury sustained while alive. I usually just cut that part out and toss it.