My 5 years old cry too when she did something wrong like hitting me accidentally. I normally let her cry out loud first before I approach her to talk about the action. After awhile I realised, she does understand she is in wrong but worry she might get scolding from us or worry she indeed hurt me badly that's why she cried. After a few sessions of such incidents where we allow her to cry out loud first before we talk to her over the action, request for apologies from her and hug to make up. She does not cry anymore and was readily accepting the facts she did something "wrong" even though she don't mean it and apologise to me. However, every child is different; you might need to find your method that work with your child.
Different child have different ways of getting them to apologies. Start soft and slow with him. Explain to him why saying sorry is needed. If he doesnt say sorry, mummy will feel hurt and sad about his actions.