I wear a medium unisex helmet too. We must just have a lot of brains. Glad you like your new helmet.

If you continue feel nausea and dizziness, I'd see a doctor. I was very sore and banged up from my fall, but never felt sick like that. I don't know much about concussions, but those might be symptoms of that.

Smart not to ride yet. As Melalvai pointed out, it's hard to scan for cars w/a sore neck -- hard enough to drive, as you mention.

Take care of yourself!