I don't know where you live, but the allergies have been extraordinarily bad this year. It is hard to say what he is allergic to at this time but I am guessing it is something in the environment.
Frankly getting into the vet is probably the best thing you can do for a hotspot. They are super easy to treat once seen but hard to get under control on your own. I have had clients struggle at home for weeks trying to get it to heal on their own; once they come in for a clip, clean,and meds its gone in a few short days and the pups feel better in less than 24hrs.
Allergies are always very frustrating and unfortunately it may always be a struggle to keep him from itching.