This happened to a buddy of mine once...
One week later. Dead.
Can I have your bikes?
Seriously, this did happen to a buddy of mine and it was testicular torsion. When your nut gets twisted around in your sack. It is very serious and hurts like hell. We brought him to the ER and they ID'd it in about 2 minutes and he was under the knife in under an hour.
If you are having sharp pains, go to the ER immediately. Otherwise doctor tomorrow.
-Z