Hello RL Shafer..
Pain in the testicular region can be attributed to:
In your post you have not mentioned about any history of trauma.
So an infective or inflammatory cause can be thought of ...such as orchitis or epididymo-orchitis
The lump in the groin area can be the inflamed lymph
Under such condition, your son need to take antibiotics along with analgesics under the guidance of a Urologist
There is nothing to worry...he will be fine.
Make sure he takes the medications properly.
Also he should avoid wearing tight fitting underwear or trousers...so that pressure in the testicular area can be prevented.
Wishing him a Good Health. Let me know if I need to clarify further.
Thanks & take care.