3 year old fell off swing-large cut on forehead. Stitched up-1 year later scar still visible. What can be done to remove scar-now or when older? Tx

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.
Forehead scar. If prominent/irregular, scar can be revised by plastic surgeon, probably best after puberty. Vitamin a lotion may help; also there are now variety of scar reduction products (patches) otc & online. Can try those first; if not satisfied with results, see plastic surgeon/ent /dermatologist for consultation.