Can't figure out how to edit my post, so adding some more details here:

no history of head injury.

this morning, I've had some slight neck pain on the sides of my neck, mainly noticeable when I roll my neck from side to side. The collision was fully frontal and my head didn't roll side to side during the accident, so it might be due to sleeping awkwardly.

I've read some material that says whiplash injuries can occur with just 5mph impacts, but I'm pretty sure that I'd be in much greater pain if I had whiplash. The literature on motor-vehicle related injuries from low speed impacts seems to be completely focused on rear-end impacts, rather than frontal impacts like mine. Could I be in the clear, even despite the fact that a collision took place?

I know that not every collision results in a concussion but the literature makes it seem like it's very easy to cause.