The white spots on the forehead are small hypopigmented macules and these are likely due to the side effects of the laser treatment. It is usually difficult to speed up the repigmentation process. However, the pigmentation will often gradually improve over time, but in some cases, they may be rather persistent.
Naevus of Ota usually requires multiple laser treatment sessions to clear. I agree with Dr Rui Ming that just using the ‘stronger’ laser is sufficient to treat the Naevus of Ota, and this usually does not lead to much hypopigmentation. However, I am unsure of your exact laser settings so it is best for you to discuss this with your doctor.