You can archive your releases on Nina on your release page by clicking Archive Release. This hides your release from hubs and your public profile, but it will remain visible to you and accessible to anyone who previously collected the release.
If you wish to permanently remove a release from Nina, please contact us.
While files cannot be removed from Arweave, releases can be removed from Nina on a per-request basis (contact us). Once a release is removed from Nina, new users can no longer access it via Nina.