2mm sublpureal lung nodule in periphery base.28/f 10yr smoker, quit 4 years ago. Found by accident on ct. Petrified its cancer. What are the chances?

Probably not cancer. Congratulations on stopping smoking! at your age, your risk of lung cancer will be low if you stay off cigarettes. A 2mm sub pleural nodule is likely benign. You should have another ct scan within 4 to 6 months to assure that it isn't growing. If it is not, you can safely put it out of your mind forever or just do one more ct scan one year later. If growing, have it removed to rule out cancer.
I bet they are low. I'll bet your physician has already told you it is probably an old granuloma. If he/she is good with just watching it, then your risk from cancer are less than the risk of removing it for diagnosis or trying to biopsy it. Here in kansas city, most of us have something like this from old healed histoplasmosis. Glad you quit smoking.