1cm nodule with minor lymph node enlargement in chest

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6 days ago I went in with chest tightness (thinking pneumonia) got a CT scan with a 1cm nodule, and enlarged lymph nodes. I am 34 and have smoked for 17 years (yes I am quiting, slowly but surely). Should I worry about lung cancer. The doc has ordered a PET scan. Any insight is always helpful.  Thanks.