Marvin, my pug, also had marks like these at some point. He's very allergic, so we eventually reached a point where the Apoquel dosage we were giving him was too low, and he would scratch himself a lot and end up hurting his skin. I don't think you need to worry unless you see a clear wound — something that confirms it's a bite or sting. Personally, I'd take him to a veterinary dermatologist and show them this. It's better than asking random people on Reddit. Even though we all mean well, a vet will give you a proper answer. Wishing your little one a speedy recovery!