What to do if i have a 2cm nodule and smaller nodules in my lungs, going in tomorrow for a pet scan. if this is cancer, how quickly will it spread?

Need evaluation: proceed with PET scan . ultimately you would need to have a biopsy of the lung mass to establish a diagnosis. if you smoke, please quit. God only knows how quickly it will spread. having said that- it will depend of the biology of the cancer- some cancers are indolent/slowly growing, and others are aggressive . PET scan will show if there is any other suspicious area- lymph nodes or organs.