Just my humble opinion here, but there are far too many variables to be answering these types of questions.

i.e. were you wearing a seatbelt.
Was there an airbag deployed.
What side of the vehicle was hit.
How heavy was the other vehicle.

etc.

Tennis ball. I know a sneeze can be powerful and I know that sneezing can cause people to herniate discs, but again the problem with asking those types of questions is that there is no simple answer.

There are too many variables.

How thick is your skull?
How inflated was the ball?
What side of the head or face or forehead or neck did it hit?
Did you jerk your neck back really fast?
etc.

There is a book called
Concussive Brain Trauma -
Neurobehavioral Impairment & Maladaptation
By: Rolland S. Parker

it might explain some of the more technical and highly variable physics relating to impact.

You can often use specific keywords and search some advertised books online.