12 year old pitching

Question
Two questions actually
My son is 12 years old and plays catcher, pitcher, first baseman.  He has been playing cathcer for 3-4 years and started pitching a little last year.  This year him and another player are our two main pitchers.  He has been practicing pitching with the team.  He complains alot of his pitching arm hurting.  He has not benn pitching very many balls at all.  So I don't know if this is just soreness that he will overcome as he continues to pitch or if something is really bothering him.  How do I know when to push him versus when to say enough is enough?  He has pain in his muscle, not in his shoulder or elbow joint.

Second question--how do you prepare him mentally for pitching.  If he starts to not pitch very well, he gets down on himself and then goes down hill from there.
Thanks in advance

Answer
I think he gets down because his arm is hurting.If he is 12 and catching and pitching that is ruff on his arm.Remember he throws a ball everytime the pitcher does. (almost) If his arm is hurting stop him from throwing.My son is 13 and plays on a 14u team. We play mainly at 90ft bases and we have done so for about a year.I only allow him to pitch two innings. He can work on his pitching without throwing in a game.My son has a good curve and change and we developed it by playing catch.You want him to have a strong arm at 16-18. If he hurts it now you never know if it will come back so take all caution.