does it matter

Stop throwing and get to a doctor first and foremost.  Where is the pain located?  Tell the doctor where the pain is located.

If the doctor tells you there is nothing wrong then don't let him pitch again until someone can get his mechanics worked out.  Throwing hard doesn't mean you're a good pitcher.  Good mechanics will help his arm (if it's not too late) and could even increase his velocity.  Bad mechanics lead to short careers.

That's the thing it's the same thing every year. The coach wants him to pitch and I'm leary of it. It seems alot of the kids I see get over pitched.Not getting him lessons has been my defense against being over pitched . But, since I've been on this website I see how important pitching is to HS and higher level coaches.Unfortunately I have no idea what makes a good pitching coach . If he does decide he wants to pitch I want to make sure he doesn't hurt his arm.

I'd have your son rest his arm for a couple weeks.  Once rested, have him work his arm into shape prior to throwing bullpens.  Yes, there is a big difference between pitching off a raised mound & flat-ground.  There is much more stress on the body from a mound, and it's escalated with poor mechanics.  It's important to find a reputable pitching instructor to help your son out...and as coach2709 stated, if the arm pain persists, take him to a doctor.

hueysdad- After your doctor's appointment (which is a necessity if there is arm pain), shoot me a PM. I know two people in Ann Arbor, both of whom played collegiately and one professionally, who may be interested in linking up with you. I don't know what type of monetary situation would be involved, but I could reach out and gauge some interest for you. They're qualified to help your son mechanically.