i don't think starting retinol this early would be good for you, especially when your basic routine are lacking ( skip sunscreen in winter, do not reapply sunscreen etc). Retinol also could cause purging, which is difficult to handle.
Most derms said topical creams don't really works on pitted scars, and it require clinical treatment.
If you are concern about acne and trying to reduce the marks, you can opt for aha, bha, azelaic acid, tranexamic acid and vitamin c etc.
but it is only my opinion. If you did plenty research and confident, i would say go ahead and use retinol carefully and moderately