My dog has red circle thing next to his butthole

Today i noticed something up with my brothers dog and after many attempts i got a good look and, he basically has a full red circle and it looks like it has a clear/red puss on it as well and its right next to his butthole. We took him to the vet, the vet is closed even though its meant to be open, so now im in panic mode because i dont know whats wrong with him and i cant take him to a vet because all vets are closed now He has been in a pool He has been in long grass He has been skooching his butt on the ground He is a jack russel

My suspicions are of the following -tick bite -anal gland problem -ring worm

I cannot add a photo here.