Even before my concussion, I had a pinched nerve in my neck which caused symptoms similar to those you describe. If you had a whiplash injury to your neck at the same time as you hit your head, it could also cause problems.

I have been going to a physiatrist at a back and neck clinic and doing stretching and strengthening exercises for my neck and low back (again, a pre-existing condition that was seriously aggravated after my concussion).

My stretching routine is fairly simple. I try to do it daily in the shower so the muscles are a little warm. I hold each stretch for 5 seconds and repeat the whole sequence 5 times.

1) chin to chest
2) eyes to sky
3) ear to shoulder (both sides)
4) turn head (both sides)
5) chin tuck (http://www2.nau.edu/~mtl8/images/the.../Chin_tuck.jpg)

If you have a pinched nerve, the chin tuck is especially important.

If the pain persists, you may also want to see a physiatrist or physical therapist. They can give you exercises to both relieve pain and strengthen the area so the problem doesn't recur.