First, obsessive worrying isn't OCD. We all have enough problems without persuading ourselves we have even more problems! As for your question, I doubt most of us on here have had brain injuries any more than on any other forum, but it would seem that if you have genuine concerns seeing a physician for a diagnosis would get you a better answer than from us amateurs. But just from being old and hearing a lot of odd things, odd things happen, so even if the likelihood of you getting a concussion from what you did is virtually nil, if you really feel you did something that is causing lasting harm, again, it wouldn't hurt to see a physician, though what you're describing doesn't sound like a concussion. It would ease your worry. As to the worrying itself, if that's a chronic problem, just because it's not OCD doesn't mean it can't be really a pain, so it might be time to see what you can do about that. Hope it turns out you just strained your muscles temporarily, as is most likely, like sleeping in an odd position.
You might of shocked your neck nerves. Causing your brain to have a whip lash.