How did Iruka get the scar on his face?

Answer 1

All Akatsuki members scratch their headbands as a symbol of defection from the village, although in Itachi's case, he was still loyal to Konohagakure, only joining Akatsuki to spy on the organization from the inside.

Answer 2

they aren't scars...they are face lines...not wrinkles exactly...let's say expression lines...he inherited them from his father

Answer 3

Iruka got his scar on his face from fending off the Kyuubi before getting dragged away.