I had fractional laser done. This is result after 3w. Will those white spots get back to dark or it will stay like that? (Photo)

It is best to discuss the results with the doctor who performed the procedure.cThe area will gradually repigmenting but if necessary the excimer laser can stimulate re pigmentation.

These white spots are not typical of Fraxel.  Fraxel Laser does not leave you a grid appearance.  I would definitely return to your treating physician for examination.  Please consult with a board certified dermatologist with expertise with lasers for the best cosmetic results.