Spot on my gyp's head

I have a rottie that got a spot on his back that started out the same way. The vet said that it was a staff infection. Gave him antibiotics and it cleared up after the second round. Any antibiotics that you get be sure to give them all or it can come back with a vengence if left untreated. I seen a dog at the vet when I took him back for the second round that was having to have about a 2 1/2 inch round spot cut out because it had become seriously infected because the antibiotics weren't given as instructed. Hope this helps.