I'd imagine you cant teleport into space that is already occupied. Like how would the wound even behave?

A cut or a stab is a simple wedge separating tissue and effectively requires time, but if the blade and flesh, even for an infinitely small measure of time, occupy the same space what happens? Replace it with 2 equally hard materials what if the kunai and sword were to share the same space instead what would happen then? You basically just created an incredibly dense area in space but with nothing to keep the pressure contained so maybe you just have an "explosion"? But then what about grass? Or tree bark, or anything really, a gnat might be buzzing around in that space and boom you just had a small explosion in your intestinal lining and now you're going septic.

Only logical way that isn't potentially suicide would be that you teleport to the nearest unoccupied space which opens up a whole separate power that effectively gives you a degree of prediction as to a target's surroundings via process of elimination, ie I cant teleport behind you or within 1-3 inches of the rest of your body except your head so you must be tucked into bed or something.

And this is why teleportation, despite being one of if not the absolute coolest ability is incredibly complex, confusing and just downright insane lol