After he's seen the doc to rule out CIs mentioned above and get a proper diagnosis, I'd be treating him right away.
Onset could give a clue in the meantime. For instance, an adductor tear is a very common hockey injury (said the Canadian, thus representing all those cultural stereotypes, eh?) If he knows the moment it happened, it's probably a tear. If he woke up with it, that may require more investigation.
A referral to a physio or male therapist if the creep factor is really an issue, which it sounds like it isn't at all. In which case, frictions, triggerpoint work and massage. (With that much pain, ice is his friend, BTW.)
If there is an area that's too close to where you don't want to be, you can always work on it indirectly (such as with PNF techniques.)
Also, to be more specific here, I never call it a groin pull. That's a genitalia euphenism. I'd say inner thigh strain/injury or adductor tear. The client will feel better about that terminology, too.
Otherwise, of course, "if in doubt, RO."