How much could I be entitled to for sciatica nerve damage from a car crash?

[Ben]

I was In a bad road traffic accident that was not my fault, the other driver was dangerously speeding and hit me with such force my car was writ off and I have been suffering back pain for weeks that has spread to my legs, I went to the hospital and the doctors told my I have sciatica nerve damage which could easily have come from the accident, how much compensation can I claim for sciatica from an RTA?