I also clicked on an ad accidentaly and reported it to google, a few days later I got an email saying Thank you for the notice and please be careful in future... No biggie...
My brother has a past experience with this accidently click. After many email to google, still google don't accept the reason. The account is still being banned. No reasonable answer from google whatsoever.
I have done this before, and I emailed Google with a very polite email saying what I'd done, that I was serious about AdSense, and that I'd try never to do it again. They emailed back in a couple of days saying that I was a naughty boy, but they appreciated my efforts, and it was nothing to worry about. Then I remembered that I registered for adsense at home, and I did the accidental click at work, on a completely different IP address! When they turn over $2billion a year, I honestly can't imagine they would ban anyone over a $0.14 click.