Next Injection?

I've had CTS tests a couple of times now. The previous time however, my test results seemed to have showed improvement but with the pain I was experiencing, I was still given another an injection in my wrist again as the previous had worn off.
The Doctor I saw said that if the pain returned again then to get in contact, not through the GP, and we could arrange another. The pain has come back again as I am experiencing the same pains as before (numbness/tingle in the fingers/trouble writing etc).
I'm not sure who I need to contact though.