Hi. Welcome to Just Answer. My name is***** Thank you for your question. Can you post the pictures with the paper clip icon?
Thank you for those good pictures. That area could be a bite or a scratch. Some will accidentally injure themselves if they are scratching themselves from ear issues, but the ear looks pretty good on that photo. Honestly, at this time with him being such a challenge to get into the vet, you could just monitor that area. In that location, a bite or scratch could just heal on its own with his functioning immune system. If the area starts to really swell, then cellulitis or an abscess could be happening. I wouldn't feel that stressing him out greatly is needed at this point. If he was easy going and easy to get to the vet, then having him seen and possibly antibiotics started would be a good idea. I wouldn't be overly worried at this point as a lot of male cats that are outside probably get in similar tussles and never have an issue from them.
I'm hoping for the best for this guy!