Wash and iron.
Stick to etiquette.
Wash it by hand with neutral or delicate liquid soap, the water should not exceed 30 °, do not rub it, massage it, do not wring it, pat it dry with a soft towel. Spread it horizontally on a towel, do not expose it to the sun and any heat source. Oh I forgot, the sweater must be inside out.
Iron it always holding the sweater inside out, with the iron at low temperature, the iron and the sweater must never come into direct contact, always put a piece of damp fabric between them, then give them a very light stretch even in the right direction, better not to use steam, if you use it, very little.