Oh dear. Sounds like Great Enemy is paying the price for his humans’ failure to keep him safe (i.e., indoors). :(.
Sounds like your pitty is doing better, otherwise I too would say take him to the vet. My cat (30 years ago, when there was less of a push to keep cats inside all the time) was outdoors one time, I called her, she came running - and ran smack into a strange cat that was hiding under the car in front of my apartment. Fight ensued… my cat came in a few minutes later, but the next day could barely move. One of her hind legs was bitten, an infection started, and her leg had gotten so swollen she couldn’t walk. Poor kitty. Trip to the emergency vet, lots of meds and a shot of a diuretic (to relieve the swelling), and within 24 hours she was pretty much back to normal. Anyway, just another anecdote to add to the “cat injuries can be NASTY” chorus.