Just had my physical, but I have to have repeat CBC due to two immature white cells in my differential. Doctor not concerned, but I'm unsure.?

Not likely a problem. Two immature white cells is not likely to be a problem. Most common causes of a left shift are infection, autoimmune disorders, or medications like prednisone. The doctor is being appropriately cautious and following it up. Rarely could be an early sign of a blood disorder which is why they are going to follow it.