Well, I guess I should think twice about jumping off a building in a dream! Wouldn’t want to wake up as a bloody mess all over the bed!
Anyway, I don’t believe it to be true. Sometimes people dream there are bugs on them, when there is, in fact, a bug crawling on them. They can feel the real bug but it doesn’t quite wake them up. Same thing with the cuts. You could scrape yourself on something while turning over in your bed for example. Or it could be a spider bite.
It’s the same thing as hearing your alarm clock in your dream as something else.
On the other hand, this might have to do with Chaos Magick. Essentially what it is is the fact that anything is possible (hence: Chaos), and with enough mental training you can learn to manifest your desires out of the chaos. When it’s put that way it sounds somewhat reasonable/possible to me.
Now perhaps if you are into a dream it could simply be involuntary Chaos Magick.
(Google Chaos Magick and look into it a bit, some of the stuff is really interesting.)