These are red, tender - to - the - touch, hard lumps in your breasts. (americanpregnancy.org)
If you notice a tender spot, redness, or sore lump in the breast and you do NOT have a fever, the most likely cause is a plugged milk duct. (motherandchildhealth.com)
At other times during your breastfeeding experience, you may notice small, tender lumps in your breasts. (verywellfamily.com)