white circle

I noticed a bump under his skin, then red spots which I chalked up to him and his brother playing roughly. Now they have a white scabby layer on them. Anyone know what this is or how to fix it?thank you!!

my beautiful little sphynx Albert has developed a strange mark on his back today and I'm very worried. As I cannot find any similar cases or get any idea what it could be! Can anyone help?!?! I have attached a few images below! Albert is 8 months old he has had all his vaccinations, His...