Sorry to hear that. Since a blow to the face is the most likely explanation for a nosebleed, it sounds like one or more of the adults had denial issues.

If things didn't go further than punches to the nose, you may be able to get one or more of the adults to recognize their mistake, now that you're also an adult. And maybe that will provide some closure for you. Just be emotionally prepared in case they cling to denial. (Which is likely.) It's not your problem. It's theirs.