Not every matter outside one's private affairs is irrelevant. Protecting others, returning rights, and helping with legitimate duties may properly concern us.
Needless intrusion: reading another person's private messages out of curiosity or circulating unverified gossip.
Legitimate concern: helping someone who is being wronged or checking on a duty entrusted to you.
The phrase مَا لَا يَعْنِيهِ concerns what does not rightly concern a person. It should not be used to avoid social obligations or silence responsible assistance.