There's an explanation for this one.  I scratched my arm a little bit, so I put a band-aid on it.  An hour or so later, it felt weird, so I removed the band-aid.  Turns out, I had developed an allergy to the adhesive in band-aids.  My entire forearm was now covered in a bright red, painfully blistered rash oozing yellow fluid.  And since I couldn't put a band-aid on that, I had to wrap gauze all the way around my arm.  It took eight months to heal, and still recurs a little bit occasionally.  So that's why I wanted the time machine.  I just wanted to stop Past Jenn Bean from applying that band-aid.  I wouldn't use it to step on butterflies and alter the course of the universe or anything.
Flourless chocolate cake is the best.  Just the best.