Little lump in teat

[victory]

One of my goats that is out on lease has formed a little lump in her teat.
The little lump is bigger than a pea, and does not move when you touch it. When I examined her yesterday she seemed okay, but it is painful when you try to milk her. This has been here for several weeks, but I just heard about it yesterday. So does it sound lie mastitis??If not any ideas?
She is a very healthy four year old Nigerian doe, she was recently bred, about three weeks ago..