My Newborn Is 3 Months Old I've Been Only Beenbreastfeeding

My newborn is 3 months old I've been only beenbreastfeeding him by pumping, 7 days ago I woke up and my right breast was so hard like a rock and I noticed a pea like lump under my right armpit that hurt, now after applying warm confesses it got down in size but is not completely gone ?also I'm trying to pump as much as I can and my breast feels soft again but I'm not sure about the tiny lump now Is this something for me to worry about