I have come across something similar to this in goats, its a form of fungal and will not go away unless you use vet pescribed medication. I do not know if this is what your pig has, nor an I saying this is what your pig has but it needs to be diagnosed properly by a vet.
Let me tell you about my experience with home remedies and I know a little more about some of the regular ailments animals can suffer with. Last year I brought spot on treatment for my pigs as they had a case of lice, I treated as per the instructions and one of my pigs suffered from what I thought was a allergic reaction to the treatment itself, it caused red, sore skin all over her body for 2 days, but better the devil you know, the parasites needed to go. It took 4 weeks for the reactive pig to recover fully and just 5 months later she developed bald spots again.
Thinking it was an allergic reaction to lice again, I used the same spot on treatment on all 4, again she reacted really badly and 5 weeks later the hair eventually grew back. When it happened again a few months later I couldnt put her through the post spot on application suffering and I thought if its lice, a shampoo would be much kinder to her, after 3 weeks of shampooing and her not getting any better, she didnt get any worse either I decided that even though it didnt seem to look like mange or lice I was out of my depth and my home solutions were not helping matters.
After advice from two members on here I got a better spot on treatment which I used right away, I also took her to the vets for a check up, unknown to me what was actually happening was she had mange mites, the spot on was partially treating them, but she was suffering from chemical burns from the inferior and unsuitable product that I naively thought would be fine for the pigs - despite it being labeled for use on guinea pigs. The treatment I had used from the advice given was the correct treatment and after a 6 week treatment course she was clear of mange mites and recovered much quicker than previously.
So even though I did all the right things with the right treatment I believed to be correct for my girl, I had caused her suffering in the process, even though it didnt look or act like mange which I have seen many times, because she was being partially treated, it never took hold like it should, but also never was resolved which it should have had I used the proper treatment. So even in my experienced hands I had done wrong by my girl and for the sake of a £12 vet visit it could have been resolved months before.
Please take yours to the vets