Is it possible to lower my nostrils after rhinoplasty?

Yes. Retraction of the nostrils, or nasal ala, is a known complication of rhinoplasty surgery.  It is certainly possible to do that and usually the revision procedure is less invasive.  The techniques for accomplishing this vary, but it usually involves using cartilage grafting; either borrowing cartilage from your septum to place small grafts along the alar rims (rims of the nostrils) or using skin and cartilage from the ear to place inside the nose to lower the ala (nostrils).  There are various techniques surgeons have, but it should be a relatively easy fix. I'd recommend talking with your original surgeon.

The increased visibility of nostrils on front view can occur with too much tip rotation or notching of the rims. The correction of this can involve surgical revision aimed at counter rotating the tip or repairing the notching. In either case, there are numerous techniques that can achieve these goals, and the best one for you would require a more thorough exam and history of your prior surgery. I hope this helps you as you begin your research of this issue.