Breast pain

My breasts were engorged last night and it was so uncomfortable I woke up at 4:30 am to pump. My LO is 3 weeks tomorrow and I got 4oz out of each breast at that session. Ever since then the underside of my left breast has been painful and tender. It's soft now (not engorged) and no discoloration - any idea what this pain could be? It's been like this for about 12 hours now.