So I was rewatching an old episode and wondered about the tiny black dot thing that Michael dug out of his arm, and gave to Lincoln to swallow so he could get to the infirmary. What exactly was it? I know it doesn't seem relevant anymore, but they never fully explained it (correct me if I'm wrong) and you never know - it could pop up again in another episode. It looked too flat to be a bullet. Did Michael have it in his arm from a previous injury, or did he plant it in there beforehand as a "just in case" plan (likely, since his tattoo seemed to indicate its exact location in his arm)? But how did he plant it in there? Or was it meant to be used in another part of his plan, and he was just desperate to get Linc out?
Was this ever explained, and if not, any thoughts? :)