I was a bully once (hurt a woman's only child) but I'm ashamed... what can I do?

Even though we're friends by now (I've changed) and 20 year-olds, I'm still ashamed of visiting him. We're in our 2nd college year and living with our parents; they pay our tuition. I'm not sure if I can even show my face in his house. I hurt her child.

The only single time I've met his mother (rightfully upset and nearly in tears) was right at the principal's office. We were 12-13 year-olds at the time and even though he had a couple other bullies, the main issue was with me. I admit to laughing and smirking at the office too, not caring about getting suspended nor her pain.

The lady obviously had a terrible image for that day. I've treated her only child horrible, bullied him even physically too, humiliated him, hurt him and laughed at that office. Even though it's been 7-8 years since it happened, for sure she still remembers. What can be done? Or do I just continue refusing to visit him and meet elsewhere.
I was a bully once (hurt a woman's only child) but I'm ashamed... what can I do?
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