How Long Does Nebido Take To Produce Sperm?

I've taken Nebido for about a year, which is a Testosteron Replacement Therapy. The last injection I got was August 10, and then I stopped taking them because of the result of a sperm count test. I had no sperm at all. 1) How long would it take for the body to start producing sperm again at natural levels? 2) Is there any danger of a lasting negative effect on the sperm production? The information I have received by my doctor is that it is only a temporary side effect, but I'm a bit worried.