In From the Ashes (2019) Agent Piper shot herself through her left hand, leaving a big hole. This episode the injury appears gone.
Mack is very large and is established to be very strong. Why doesn't he just pick Flint up in a fireman's carry to transport him? It would hurt Flint, but not as much as trying to walk between Yo-Yo and Mack, putting weight on the leg and being unevenly supported.