So that left rear leg does look like it has two things going on (in my non-professional opinion)
1. A deformity from birth. That left outer growth appears to be almost like a dew claw. It has white hair around it as well. That's why it looks like something form birth.
2. An infection of a wound below the tarsal gland on the inside (or maybe an infection of another dew claw). Tarsal glands are covered with all sorts of bacteria. My hope/guess would be that this will heal over time.
I wondered about the broadhead as well. Here's a vid over a week later. He seems to be walking better but maybe the previous one he'd just got up from a nap or something.