Your symptoms are suggestive of post inflammatory hypopigmentation which is very common after laser treatment. The pigment-producing cells (melanocytes) are damaged or destroyed in the healing process of inflammation.
Other causes may be pityriasis alba,pityriasis versicolor,vitiligo and nummular eczema. Skin scraping for mycology and/or biopsy for histopathology may be necessary to differentiate them.
There is very little that can be done in post inflammatory hypopigmentation although with sun exposure the white areas should eventually repigment.Pls apply a sunscreen with spf of atleast 15 half an our before going out in the sun.also pls don’t apply any benzoic acid or corticosteroid cream as it may further aggravate the problem.
Hope this helps.Take care and pls do keep me posted if you have any additional doubts.