Cigarettes is it possible, I have cancer? or have done permanent damage ?

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I've smoked a few cigarettes is it possible i have cancer? or have done permanent damage ? I am 22 and have smoked probably about 20 cigarettes in my whole life, which is two packs i think. Im not addicted, so i thought i shoudl quit while i was ahead, so i ended up quitting a few weeks ago. i was just wondering if by smoking these cigarettes, even as small amount as it is, could i possibly have lung cancer? the only thing that is leading me to believe this is my paranoia. also is there anything i can do to help heal my lungs, (drinking water?) my father has smoked unfiltered cigarettes for over 20 years and does not have cancer so im hoping that uit would take more than 40 for me to develop cancer. and please ddot write an answer explaining the danger or smoking and how i should quit, because im aware of the danger and i have quit.