* Not serious: The damage is limited to the surface and doesn't affect deeper tissues, bones, or organs.
* Temporary: The injury is expected to heal quickly without lasting consequences.
* Not worth worrying about: It encourages someone to be brave or not overly concerned about something cosmetic.
Examples:
* After a small scratch: "Don't worry, it's only skin. It'll be fine."
* About a minor scar: "It's just skin. It doesn't change who you are."
* To encourage someone facing physical hardship: "Come on, get up. It's just skin, you can push through!"
In essence, it's a way of saying "it's not a big deal."