I guess I can stop punishing my son.
Why don't you want to punish your son further?
He's already depressed and crying and I feel too sorry for him
If you feel as if you've punished your child appropriately enough already, then its okay to not continue further. It's good to be aware that you may be going too far and showing restraint. If you weren't, you might hurt or upset your child more than need be.
I don't need you to tell me how to parent my own kid.
I apologize, I am just giving my perspective on what you told me. You are free to parent your child whatever way you please, just as any parent is!