Damage like that would probably cost as much to properly repair as it would take to build a new sub.

I’m not a submersible expert by any stretch, but given the visible damage it’s a safe bet the pressure hull has been damaged and possibly punctured. In US subs the pressure hull is cast as a single piece, but I believe Russian ones are two pieces welded together. Whatever the case, damage to the pressure hull is far from trivial to repair. Any repairs to it that aren’t a complete replacement will likely result in a significantly weaker hull, meaning it could no longer safely dive as deep as it used to.

And replacing it would mean almost complete disassembly. Probably safer and more cost effective to build a completely new sub and cannibalize any parts from this one that makes sense.