If it is just a single click than it won't be a problem until or unless you belong to an Asian country. Google seemed to be pretty strict with the Asian countries when it comes to its Adsense policy. Just make sure that this thing won't happen again in future, and there is no need to contact them, everything would be great, but if you do than still there won't be any harm, they might appreciate you for that! So it is really not an issue if you want to contact them.
If it happens by mistake then that is bound to happen at some point or another but I wouldn't risk it by clicking on your ads because it is not worth being banned from adsense. Focus on the quality of the content of your website and you will see your traffic increase.