Might be that he dont have the courage to talk others and hesitate in making new friends. We can talk to him about his likes dislikes and maybe be good friends with him and slowly encourage him to open up to his friends parents or maybe his teachers who will understand him and will help him to overcome his fear.
I should encourage him/her to be free from all kinds of tensions and always be optimistic.I should also told her to share her problem with friends,parents and teachers who will not help her to solve her problem but also will help her in her work.