His stuck shed was due to a minor injury there that had a scab; it's typical for such a thing to come off with each shed, but it's small enough that hopefully it won't be
noticeable forever. It's not rare for snakes to rub their heads when pushing on the tops of their enclosures, for example, or something abrasive in their furnishings, &
some BPs are left with noticeable pinkish-white "bald spots" on top of their heads from rubbing...the scales may not come back all the way, especially if it's larger.