4 months post fractional CO2 and my skin has become evenly dark and tan looking in the treated area. What can I do? (photos)

It started about one month after the treatment. I noticed my whole face looking tan and it was the dead of winter when I have minimal sun exposure. It soon became clear that it was the treated area getting darker. The untreated areas around the eyes kept their normal skin tone. I also still have vet fine grid patterns that have not totally faded. What could the darkening if the skin be and how could it be treated? Should grid pattern be gone? Doctor advised continual sunscreen.