Hey Kube, I have had pain in my testicles for many years prior to starting finasteride. As you say it does hurt when they are manipulated and I have been to the doctors a number of times because of it. I had surgery done to repair a varicoceale when I was younger and this helped decrease the frequency of painfull twinges. For me I know that I have always had sensitivity with the boys (more so on the left side) with that being said I did notice some very mild discomfort whithin the first week of using finasteride.
Perhaps your pain is not from finasteride but from something similar to what I have experienced.