When Ruca was in training to become a wood-warder he was up in the trees and had his first Echo Moment that scared him so bad he fell out of the tree and broke his leg in three places. He has a big scar on his right thigh where the bone broke thru his skin. This is his only scar as he would -

Become so terrified of being hurt and dependent on another to take care of him again that he specifically learned how to heal so he could protect/help himself. So now he heals any wounds/marks/etc immediately because he hates his scar and sees it as a sign of weakness