Google adsense prohibits publishers from clicking on their own ads for any reasons. But it some times happens that publishers (bloggers) click on their own ads accidentally when they are customizing their blogs.
I also did this once, when I was a beginner on adsense and I was scared as hell that Google will terminate my adsense account. If this has happened to you by mistake of cause here is what you should do:
Send an email to Google adsense support or to the email address that was used ti inform you that you have been accepted to adsense,telling them of the accidental click. Provide them with the URL of the advert that you have clicked on and also provide them with your blog/site's URL. By doing this you will not be kicked out of adsense
N.b clicking on your own once will not automatically get your account disqualified from adsense.
After doing this you can for curiosity sake check how much the advertisement was worth. Now do not do this on purpose