Son is nail bitting

My son, who is 8 years old, has recently started to bite his nails; at times, he is also peeling cuticles and skin of his fingers. I think it’s a direct result of anxiety; I’m seeking psychological help. I want to make sure that I do not add to his worries.

Can you help with my T line specifically in both models?

Unintentional Model
C: My son is biting his nails
T: He is hurting himself
F: Hurt
A: Try to stop him by shouting, yelling, scaring him off, he stops momentarily, but he starts doing it again in sometime
R: He is hurt

Intentional Model
C: My son is biting his nails
T: What help can I offer
F: Love
A: Ask lovingly, “what are you thinking. Is there anything that you are not sure about and want to talk about?”
R: I’m helping him