To be on the safe side, handwash it in detergent especially for delicates and wool.
Use hand-hot water and very little detergent (if you have too much soap, rinsing can take forever).
Be very gentle, caressing rather than rubbing, and rinse really, really well until the water is completely clear (fill the bath if it’s easier). Squeeze out as much water as you can then lay the jumper between two thick towels and roll up. Leave somewhere warmish such as the airing cupboard and check progress after 24 hours – it should be almost dry.
No need to iron!