Hi, Welcome to HealthcareMagic!
You were probably born with a birthmark; birthmarks are of many types & some may be regressive like hemangiomas (though not all types), progressive or static, increasing in proportion to body growth. With limited information like "a large scar", I may state it could be an icthyosis hystrics, or verrucous epidermal naevus etc. These congenital conditions are due to embryogenetic 'mosaic' anomalies & are usually not correctable. Still I advice you to consult a dermatologist
for at least a proper diagnosis & let me know.