From what age should you start punishing your child for wrong things he does?

I wouldn't go with punishing as it would be detrimental to the child's psyche — it might inculcate resentment in the child, he might become aggressive, and knowing the nature of punishment, would dare to test your limits. Instead, try to logically reason out to your kid why something they did was not right. Make them understand how they would feel if someone did to them what they just did. It takes time, so you have to be patient but it is worth all the efforts in the long run.