Yes, but that's simply something that I choose to not be a part of my headcanon. Sombra having the capability of healing an injury without any effort or hindrance just seems a little ridiculous to me, so I don't apply that to my AU. While I think that he does still have the ability to heal himself, he needs to put his magic to work and extract the essence of varying amounts of crystals to apply to his wounds. And the reason for why he clearly hasn't done this for his horn in this AU is because he doesn't live in the Crystal Empire nor in a location where there's an abundance of crystals, therefore he's very selective in what he decides to expend limited resources for.