Spider bite? Found sore on my dog

2 days ago I found a sore on my dogs hind leg. This is what it looks like.Now today I was doing yardwork and almost ran my head right into a black widow, the widows web is right near where he uses the bathroom, although the web is at about my chest height , so Im unsure weather that could be what it is. Hes on s leash when I walk him, and not in an area where I could really see anything puncturing him. Could it be a widow bite or just a wound. How do I clean it, care for it. I read no peroxide, do i just use water or is there something I can do for it?

Could be a Tick.

I would be asking my vet's advice.

I still don't know what had bitten my dog's ear that it got swelled horribly. Its ear was operated which made my dog very weird (a dog with one ear clipped).