I'm very sorry to hear that. If you really want him to know that you're sorry, you can try to find other ways to tell him. If you know his address, you can send him a letter or an email if you know his email address. You can also figure out if he has other social media accounts that you can DM. If you cannot do any of this, why not try to meet him in person? Or ask his friends or family for help? Just make sure you tell him how sincere your apologies are and promise him that it won't happen again. I hope this helps you and that everything would be better between you and this boy.