Pain in left breast, stopped breast feeding 3 weeks ago. Hurts to lie down or touch or carry my baby on left side. Boob is sore.

See below. See your ob. You may have a mastitis and need treatment.
Pain. Pain may be because of engorgement or infection. Would suggest seeing a doctor soon to check to see what medication you may need.
Mastitis. It is not unusual to have mild pain when you stop breast feeding. However, if this is moderate to severely painful, your breast is red or you have a fever call your ob. You may have post partum mastitis, and may need an antibiotic. If you are unsure, it is best to see your ob. Feel better, best in health.