1cm ground glass nodule rll. pneumonia in october 2014. 42 yo male with no hx of ca. 1ppd smoker x 20 years. should i be concerned for cancer?

Possibly: ground glass nodules, particularly in current or former smokers need to be evaluated. Depending on its density, a PET scan may be helpful but at a minimum the nodule needs to be proven stable in size for a period of two years to assure its benign. You need to see a pulmonary MD to have it evaluated as some require resection to know the diagnosis.