Bro, no kidding here, if the testicle that hurts begins to grow in size AT ALL, get yourself to an emergency room. Not a family doctor, an emergency room. It could be a testicular tortion, which is caused when a testicle rotates just enough to cut off its blood supply. It will begin to swell within minutes and it not treated within hours, you will lose it.
I'm speaking from the voice of experience here. Six years ago, I crossed by legs awkwardly and felt a sharp pain, but thought nothing of it. A few hours later, my right testicle had doubled in size, but I thought I had just bruised it. A few hours more, and it was the size of a grapefruit. By the time I got my stupid ass to my urologist, who tested by placing a powerful microphone on the testicle itself, the testicle was dead. No heartbeat could be discerned because circulation had been cut off. I immediately underwent surgery to check out the situation, and when I came out of recovery, I had only one tesitcle.
That's right, I admit it, I've got only one ball. I'm telling you this in the hope that knowledge might prevent someone else from needlessly going through what I did.
TAKE CARE OF YOUR NUGGIES. I wish I had.