I've been bitten like that before. I had a huge male rescue BP that was not only improperly fed (thus hungry all the time) but was an elementary school "pet" and previously to that had lived in a frat house. You can only imagine the temperament on that guy.

In the year I tried to work with him he bit me.....I don't know how many times. About 6 months in I was at the point where I could wear gloves and feel kinda o.k. handling him. We were doing some basic socialization work, and he started nosing around my arm. I thought to myself "this dude is gonna bite me." And he did, big time, and coiled up so tightly my hand went numb. It took 2 people other than me, 2 credit cards, and some cold water to get him t let go, and it still took at least 10 minutes. That guy was not messing around.

After that day, it went seriously downhill. I could do nothing with him. He would launch himself at anyone that opened his tub and he was so big he was very difficult to control safely. He wasn't a happy snake, and was dangerous in a household environment. I called some places, but living in Maine there aren't a lot of options for ornery BPs. We eventually decided to euthanize him, as his behavior was getting worse and not better : /

None of my 'normal" snakes have done this, but when I see any of then slow down and start nosing around my flesh like that, I calmly redirect their attention and put them back in their house.