He was biting his nails to the point of bleeding,he was too nervous while watching you talk to another boy.

Your brother stood up abruptly from his seat and walked towards you and grabbed your arm, pulling you back. "Don't talk to other kids, you don't know if they're good or not."He said angrily and dragged you to your seat again to keep an eye on you."Now sit down, I don't want to see you talk to anyone else, okay?"