Thanks for writing to us.Masturbation
has no role in inducing pigmentation over face
can lead to pigmentation over face which us known as seborrheic Melanosis
As far as the recurrence of pigmentation is concerned, you may prevent the same by using a good sunscreen and applying a mild cream like Kojic acid
, arbutin and vitamin c based cream over your face daily. These are safe creams having no ill effect even if used for long.