4th level-5th level, probably 4th level
The 3rd level spell Thunder Step from Xanathar's Guide to Everything allows a caster to teleport up to 90 feet, optionally with an ally, and deal a small amount of thunder damage to everyone within 10' of the point of departure.
This is a reasonably good approximation of your spell, except that your spell does, in effect, a lot more damage, affects only a single opponent, has a larger range, and doesn't usually leave you in the midst of the enemy. You spell should probably be a higher level than Thunder Step.
The 7th level spell Plane Shift from the PHB allows a caster to instagib more or less any opponent by teleporting them to an appropriate instantly lethal planar location. For enemies that can't cross planes, extensive planar knowledge is not required. The spell can instead be used to escape nearly any situation with or without your party and/or attached NPCs as well.
This is a better version of spell, except it does a better job of killing your enemies or saving your butt but not both at once, and it requires touch range, and it lets you fundamentally alter the nature of the game by accessing previously inaccessable realms at-will. If it weren't for the unparalleled utility aspects, Plane Shift would probably be 6th level. Your spell is not as powerful as our pretend same-plane Plane Shift, so it should be a lower level than that.
There aren't really any spells to compare against in the 4-6th level range. 4th and 5th level spells are 'normal' spells in the game system; PCs get more than one of those per long rest and features that do stuff with spells are often limited to these magics. 6th level spells are basically a separate higher tier of material.
Your spell doesn't feel like a higher magic spell; it isn't fundamentally changing the nature of reality, its effects don't persist necessarily for very long, it doesn't wipe out a whole group of enemies or do pretty much anything on the level that 6th+ level spells tend to do. It does let you reliably kill a single target that has a low WIS save and doesn't want to be in melee with the party and doesn't have friends, and targets really close to a super-deadly hazard like a very tall cliff (20d6 damage) or a pit trap with poisonous spikes and a black pudding in it or a sphere of annihilation or whatever, but that's not letting you do anything a PC couldn't conceivably accomplish with a really good grapple modifier and a bit of time.
Basically, I don't think it should be 6th level. As for 4th or 5th level spells, it's kind of a grab bag. I think it should be 4th level, like Banishment and Dimension Door, because having to swap with an opponent means you often have to be in the middle of the enemy force afterwards, and that's rough for most characters. Eldritch Knights also get 4th level spells eventually (19th level) and this seems like a spell that they should be able to at least theoretically cast. 5th level spells, like Bigby's Hand and Cloudkill just subjectively appear more powerful than your spell to me.