Take him to the shelter and see if they’ll at least take a look. You probably don’t have to surrender him if you don’t want to. A lot of rehab places do have medical experience though.
I’m new to chickens but I really don’t think this is coming out as much as it is something that went in. I have never seen a bone with a color change like that and no blood. Since you can move it, have you tried pulling it out? Check out Flying Nun Farms thread about sugar for wounds. The...