My dog has this right at the base of his tail but underneath, so near his bottom. Not sure how he got it but maybe brambles catching him or a bite that then irritated and his licked and nibbled it. I've had him in a buster collar and cleaned with hibiscrub and kept dry and all was well. Left buster collar off today and he didn't touch it, it was dry. did our normal routine walk and left him to sleep, he's been in the garden with us and I've just caught him having a go at it again.
It has spread down the back of his thigh a bit and is very superficial. Looks like small open grazes.

I've cleaned with hibiscrub, put on drying anti septic powder and have given antihistamine to help reduce the itchy irritation, is there anything else that can apply that might help heal it quickly? I will go to vets on the Monday if not better. Just annoyed with myself I didn't leave collar on for a bit longer, he's had it for about 3 days but it was much better.

Other than Hibiscrub which I have used, diluted, for this (and antiseptic powder), I have also used a diluted salt solution.   And clipped back the fur from around the area if needed.   You may find your boy would benefit from an anti-inflammatory shot and antibiotics to aid healing if it's that bad.

I have cut a bit of his fur as it's long but I was reluctant too in case I show him but this is less likely at the moment as he's not a dog that enjoys it much, so I think I will shave it so the fur doesn't get caught in it and then pulled any healing scabs off.
Some site I looked at said about using apple cider vinegar with mother which I have so may try that later, it didnt say to dilute but I think I would.
I have metacam so could also give him a dose of that as thats anti-inflammatory

I would shave as it allows the air to it, which really helps it dry out.  Opi had two or three and the best thing I found was veterinary wound powder.  Antibiotic and dried them out nicely.

Calendula cream is excellent, you can get it from Boots.

You could try the spray on wound healer.  I get mine from hyperdrug.  Used on completely dry skin, so hibiscrub to have dried out totally.

Hi, I had same with my dog not long ago and read about apple cider vinegar, this aggravated it to weep and spread fast!  Instead used colloidal silver spray, the amber one, cleared the whole thing up fast!

Its drying out now, shaved more fur. I think as it heals its itches so he nibbles at it. He's wearing his t shirt onesie indoors as he was getting too hot with collar round him.
I did use apple cider vinegar once, diluted and seemed ok.