Jerked neck forward in a.M. Pain increasing with numbness in la, esp. Little and ring finger of lh. Pain moderate-severe. Should I see a doc? When?

Yes. I would go see your doctor after a few days if pain does not resolve. Also if you develop weakness or loss of bowel or bladder function.
Injury to nerve root. Since you have neurological symptoms after an injury, you should see a neurologist to evaluate the extent and exact cause of numbness.