Rear wheel sideways "play"

warranty? after a week it should not do that. ...unless you got a unipac/create then you already exceeded the lifespan of it by factor two.
Bike was bought from UK, I'm in sweden. So, I'd rather try fixing it myself. It's a KHS Flite 100. Noname (?) hubs.

What does the bolt closest to the wheel do? Should this be tightened? Any recommendation on a tutorial for "repackacking and retightening of the wheel bearings and axle nuts"?