50 year old male, just found a 2cm lower left lobe nodule on xray, awaiting ct results. quit smoking 19 years ago. should i be worried?

Need more history: What lead you to have a Chest X-ray done? Do you have any chest symptoms? Is the nodule in your lung calcified?(if it is, it can be a benign nodule, often called granuloma. Otherwise CT confirmation is necessary; this may be followed by a needle biopsy to rule out cancer. But it can still be benign(non Cancerous).

Lung nodule: If you happen to have older X-rays or scans and the nodule was already there several months ago/ previously you can compare nodules and if it has not grown in size then it is possibly benign. If it is growing , then at its current size of 2cm, definitely try to get a biopsy or get a followup film 1-2 months later.

Pulmonary nodule: I understand your concern. Commend yourself for not smoking for 19 years. Believe in Healing Powers of your body if you have not had respiratory symptoms. Most solitary pulmonary nodules are benign. Likely to be benign if it has smooth round border, is completely surrounded by lung parenchyma, does not touch hilum or mediastinum Discuss this with your Surgeon and Radiologist and need for Biopsy.