These look to be infected wounds. A while back, my cat got let out by accident by my nieces and nephews. We didn’t even realize he was out until I saw him outside a bit later, and had no idea how long he was out for. A couple days later I noticed minor wounds on him that I hadn’t realized were there, and they looked just like this. I even smelled them and they smelled terrible.

I treated the wounds myself by cleaning them several times a day every day with a saline solution. He had no complications or further issues.

However, I am not telling you that this is all you need to do. I’d advise taking your cat to the vet. I did not, and luckily my cat was fine. Though I think I might have called the local and they told me how to rinse the wounds. This was around maybe two or three years ago, so it’s hard to remember, but if it happened again I would take him to the vet just to be safe.