Thank you very much for the useful information.
With a negative history of smoking; and the fact that none of your parents had it, its extremely unlikely that this nodule represent a lung cancer.
Moreover you did not lose any weight; and do not have other symptoms suggestive of lung cancer such as coughing out blood (hemoptysis).
Infact in over 99% of the cases, such pulmonary nodules turn out to be of benign nature. This simply represent a calcification, granuloma, or an old healed lesion from a previous chest infection.
Therefore, stay relaxed and do not panic.
At your age the possibility of cancer is least likely; with no symptoms suggestive of cancer, no history of smoking, the chances are almost negligible.
To be absolutely sure about this, your doctor may order a CT scan of the chest which will rule out any serious possibility like a cancer, and will help put your mind at ease.
My goal is to provide you with Excellent Service - if satisfied with the response, Please do not forget to Rate my service as this is the only way i get credit for my time and expertise on your question.
If you feel you have gotten anything less, please reply back, I am happy to address follow-up questions.