Just an FYI, OP. Skin cancer is a different animal than the internal cancers. Radiation will cause burns, but they're weird—the effects are cumulative. Basically, you go a few weeks, and it's all, "Hey. This isn't so bad." And then, the burns start to develop. They are annoying as fuck. Depending on where they target the radiation, there could be involvement of the inner thighs, the anus, the area around the penis—it really does depend.
I see you're dealing with an HPV related cancer. I had anal cancer (also squamous cell) with some perineal involvement. Mine was stage IIIa, so it also involved lymph nodes. If there are still cancer cells there, they will basically melt, which is incredibly unpleasant, so it's better to be prepared. If there *is* an issue, you won't want to be traipsing around your local drug store in those moments.
Get a sitz bath (or get one of those heated, toilet seat bidets), in case the anus is involved. Unscented colloidal oatmeal is great for baths. Or just prepare to take long hot/warm baths. Those really got me through. Basically, my entire groin area burned and peeled. It wasn't fun. I needed opioids (and herbal remedies, which I had to find since I don't use that sort of stuff). The pot really helped keep my opioid usage to a minimum. It was not legal at the time, so I had to go underground!
The BEST thing ever (for me) is called Domeboro. I would COVER the couch or my bed with towels and dissolve the Domeboro in warm water. Then I'd take 4x4 gauze (not sterile, so I'd just get a big box), soak it in the solution, and cover the burned areas with the gauze Then I'd lay back, relax, smoke, and watch stupid TV shows. It really helped with the pain.
I don't want to scare you, but being prepared (thanks to a friend who had gone through it before me) was absolutely the key for managing the pain and wounds. I'm definitely going "worst case scenario" with my advice. Because of the cancer I had, they went at me pretty aggressively. I had radiation three times a week from October 2013 to December 2013. And I'm still alive & kicking and cancer free.
Good luck to you, OP. Cancer fucking sucks, and I'm sorry you have to deal with it. But you've got this, and it sounds like you've got the right attitude to get through it.