in your case has resulted in post inflamatory hypopigmentationwhich means spots of lighter colour than your actual colour . post inflamatory hyperpigmentation
can also be seen as a result of sunburn.
avoid further sunexposure till the patches heal
since u have not mentioned the exact site, size ,extent of the lesions it may take approx about 1 month to regain normal colour.
use sunscreen regularly during the day time .repeat it every 3-4 hours in the day
cream over the patches twice a day for a week to 10 days.
if the colour is not regained in 1-2 months then you can add tacrolimus ointment
hope this adresses your concern