Should I also make my child say "I'm sorry"?

This involves both values and developmental stage. In common: making them say it in form alone rarely sinks in if the meaning isn't understood, and if it's tied to scolding while they don't understand, it can cause confusion. What matters more than the words "I'm sorry" is conveying "the other person felt bad" and "next time do this" in a form the child understands, little by little. As understanding grows, the meaning of apologizing grows too. What the family decides: whether to prompt the words or show it through action is your choice, by your views and the child's stage. A guide: "does the child understand what was wrong?" Aim to grow caring for others and the "next action" more than the "form" of apology.