On a theoretical level, you're correct. On a personal level, the nose thing is pretty convincing. Give it a go, you'll see what I mean.
At some instant you are reeling from a punch to the face, and you have an awareness (a memory) of having asked for it 5 seconds previously in a heated philosophical argument. The problem is you have no way of directly experiencing those previous events from 5 seconds ago. It could be that the universe is just a snapshot of this precise moment, which includes sensations of memory, the appearance of slashdot, and the fear of being punched in the face.
There is no disproving this. But it also doesn't matter, since if nothing else the present does contain the perception of continuity, which is all that drives our choices even if continuity does exist. If we somehow discovered that we're just a dream or computer simulation, what does that actually change? What previous theory of existence does it displace?