Well, after strenuous activity it's always possible to have pains. On rare ocassions I may get shooting pains in my left leg from strenuous exercise the previous day.

However, there is no real way to diagnose you over the internet as only a doctor can tell you as it could be many different things. Pain in the testicle could be epididymitis (infection of the epididymis), varicocele (varicose vein of the testicle), etc. I have a varicocele which can cause pain or discomfort and it also seems to create pain in my leg at times as well. When it was bad, my leg hurt as well. It's not a bid deal, not deadly or anything and can be fixed through surgery or embolization. It may cause infertility, but that's reversed with the surgery. It is also most common in the left testicle, but so are other problems. I've written about some alternative healing methods in some threads on this board (search if you're interested). They're based on healing varicose veins.