Sounds to me like he had your neck stacked on top of his arms, and when he pressured through it ended up cranking your head back. It's real easy to turn and arm triangle into a neck crank if you're doing it from a top position. You're probably going to have to take a load off for a few days.
It doesn't matter if you agree or disagree
... As long as I don't bore you and I spark a moment of thought, my goal is achieved
Queng leon queng tigre ecu tacacut, queca pa? - Pampangan Mandarigma Motto