My toddler has a scar on forehead. When will it disappear?

Give it 2 years. Wounds increase in collagen for 6 weeks following injury and thereafter enter into into the maturation phase when wounds subside and generally decrease in appearance. Topical silicone sheeting and avoidance of sun exposure may help to expedite the phase and improve scar appearance. While 90% of this process is completed by 3 months, with a good estimate of the final appearance, it may take 2 years.