My little boy came to me the other day and said that he had a knot in his left breast that was very sore. I felt of it and it is about the size of the whole nipple area. It has been one week and he now says that it is not sore anymore. My husband just brushed it off as puberty. Should I be concerned?
That's perfectly normal for his age. The hormone interaction in puberty can cause it just as baby boys sometimes get enlarged breasts in the weeks after birth.
I'd bet it's a swollen lymph node. They tend to hurt for a few days and then sometimes lose their tenderness. Apparently swollen nodes are very common in children. If it's stuck in place or feels very hard (like a rock), definitely get it checked out by a doctor.