CONTAINS SPOILERS

It's possible to change your appearance & stats later in the game. Early on you can use the mirror (Dressing Table) in Fia's room at Roundtable Hold. Later you'll have to defeat Rennala, Queen of the Full Moon located in Raya Lucaria Academy in Liurnia of the Lakes. She also grants the ability to respec your character and change all stats via process called Rebirth that requires a Larval Tear.