Infection, possible hernia or the start of a a bladder infection can cause pain. Also what is known as testicle torsion which can be common in children too. Since it's been over 24 hours I would have him seen vs waiting till next week at this point just to be on the safe side, since an in person evaluation should be done.
Best of luck, Hope this helps, If you need anything else please feel free to ask. If you found this helpful don’t forget to click the *accept* button!