Cable sheath damaged, cable core filling and conductor insulation intact

Yesterday I chased into the calcium silicate block of an interior wall for the flush-mounted cables behind the soon-to-be-installed sauna insulation and paneling, and in a distance from the flush-mounted boxes, where I no longer expected or searched for any cable, I slightly cut (2cm) the sheath of a NYM 3x1.5 cable. The void filler is intact, as are the conductor insulations to that extent; the cut really only nicked the sheath so that you can see the void filler (see picture). Is this a) a real problem because chemical reactions between the void filler/conductor insulations, calcium silicate, and moisture or the gypsum with which I will close the chase again may occur that could endanger the conductor insulation, or b) exclusively a problem from the perspective of the VDE or our insurance in case there should ever be a problem with the cable in that area, because the sheath in an otherwise dry environment actually only has the task of mechanical protection but must still be intact according to regulations, or c) both, or d) neither? What would be a VDE-compliant solution if it were a problem? I could detach the cable from the rest of the wall and apply a heat shrink sleeve at the spot, or—somewhat more elaborate because I would have to chisel out some space for it—a cable joint sleeve. If anyone feels compelled to give lectures on electrical installations beyond my question—the electrician will see everything and will connect the sauna stove in the end, I just don’t want to pester him with questions every other day on the way there.

If the wires are undamaged, then heat shrink tubing. With self-adhesive inner coating is the best and safest option.

Whether the veins are intact cannot be determined there. Given how deep the cut is in the rear area, it would be a miracle if at least one vein insulation hasn't been damaged. But ultimately, everything you do now without replacing the defective piece is botching.

It would be like showing a car mechanic a picture of a tire with a crack and asking if you can still easily drive at 200 for 5 years with it. What is he supposed to say? Of course, he says, "Buy a new tire, anything else is botching." And not advise to stick a bicycle patch on it.

Do you seriously want to risk a house fire to save the 50-100 EUR to have it properly repaired?

And I can't help myself... But just imagine if that were a gas or water pipe that you scratched. You certainly wouldn't think to just fix it with a little sticker, would you?

Why does everyone believe with electricity that it’s okay to do it just like that and that the VDE regulations were created by absurdly overcautious hypochondriacs who don't trust their own shadow... why is that?

It all makes sense and is based on decades of experience and analysis of damage and fires...

And I can't help myself... But imagine if it were a gas or water pipe that you had scratched. You surely wouldn't even think about just patching it up with a little sticker, would you?

Yes, if I scratched any patina or purely decorative paint on a gas or water pipe, I probably wouldn't even patch it up with a little sticker. I'm that strict. That the cores are not damaged can be clearly seen here on site, since not even the filling is scratched. I also explicitly wrote that, but the German schoolmaster in you obviously felt the need to lecture, with comparisons of apples and oranges, car tires and cables – pointless and regrettable that you spent your time on such comments. Our electrician sees absolutely no problem in the scratch on the sheath, as no forces act on the cable at that point, and would accept it from us as is; I nonetheless decided to simply replace it completely, since it was much easier to access both ends of the cable than I expected.

One should not ask if one does not like the answer and you know better anyway, even without being an expert.