Strange Spot on BP scales?

[zwums]

My male (as best I can tell) BP is about three years old, which is also how long I have owned him. He is my first herp. He's been a great snake. I have him in a great set up, a 45 gal tank. He has a heat mat and a heat lamp, with temperatures in the mid-high 80's on the warm side and high 70's in the cool. Humidity is mid 50's. A large water dish for his drinking and the very rare soak. He's always active at night, knocking his hides and furniture over. I handle him about 4 days a week, leaving him alone the day of his feeding and the two days following. While being handled he is very adventurous and not at all timid and if I'm warm enough, loves to sleep against warm skin. I clean his tank pretty much as he poops, picking up and putting a bit more bedding in the mix (aspen shavings.) He eats very regularly, with some skipped meals at winter time and before sheds. As far as I, an amateur with reptiles, could tell he seems perfectly happy and healthy.
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Until this week. I'd been handling him less due to the stresses of moving which have kept me incredibly busy. That's when I notice this. I'm sorry for the size of the photo. The spot isn't fuzzy, there is no liquid or discharge. it is like a half an inch from his head, where the neck is still pretty thin, as you can see in the image. The scales are wrinkled and slightly discolored. The spot is a little smaller than the size of my pinky nail. I am extremely worried. It had to have developed in about a week, because that's the longest I went without handling him. The spot is slightly rough. Touching it garners no reaction from him whatsoever. His behavior has been perfectly normal. I need help. I'm worried sick about my little guy. What is this? And waht could have caused it?