Hotspot on his back

A couple of days ago, I noticed some yellow fur on Troy's back and felt what I thought was a scab.

Today I had a look at started cutting the fur away a bit to be able to see better. I soon found a weeping sore and ended up shaving a large square out of Troy's fur on his back which revealed a very sore and red hot spot.

I cleaned it all very thoroughly with hibiscrub and will see how it goes. If it doesn't improve within a few days, then we will have to go to the vet to pick up some antibiotics.