And do you swap places with matter at your destination or just fit your pieces around and into whatever is already there?
If you don’t swap, you could end up with air in your blood stream and bacteria and fungal spores everywhere. And a chance of nuclear fusion depending on how close atoms end up to each other. And if it can fuck with things at a nuclear level, it will also fuck with them at a chemical and structural level.
Or if you do swap, it becomes a powerful weapon where you just pop into someone’s body, putting the parts of them you overlap with where you used to be, then you just pop back out in a different spot. Bank vault door is too thick? Just teleport multiple times and you’ll get through safely as long as you can remain pretty still while going through it. If you can constantly teleport a tiny distance, you might be impervious to all attacks because stuff would get swapped before it impacts you, but that “might” is doing a lot of lifting. Though you probably also wouldn’t be able to hear sound, so you would be vulnerable when having conversations or listening to music.