Extinguishing cigarettes on your hand, before trying to quit them?

Sorry if the title is confusing, I am not sure how to phrase it.

I am a smoker myself, although not a really regular one, and something caught my attention that I can't get it out of my mind. I was watching House M.D, when in one of the episodes dr.House figured out a teenager was a smoker trying to quit, after seeing a burn scar on his hand (Season 2 episode 12).

I know a lot of people who are also smokers and none of them have something like that. I might have misunderstood the episode, but it never seemed to be suggested that he was abused or forced, only that he was a regular smoker having a hard time quitting and going cold turkey.

So my question is more, why would he have such a scar? Is extinguishing their cigarettes on their hand something people do while trying to quit, or something stupid American teenagers do?

This has really been bugging me, as I don't see the logical conclusion.