I think the most likely avenue would be an application of reverse cursed technique. [ aka, that thing he doesn't know how to do yet. ] My teacher used to explain cursed energy as being like electricity -- it's powerful, but hard to control, so we run it through a technique to create an effect. Reverse cursed technique is like...forcing the current to go the other way. The negative energy becomes positive. A skilled sorcerer can use that to heal themselves.

[ ...more skilled than him, unfortunately. He's talented, but he's still a first year. ]