Mastitis is a bacterial infection of the breast. Your breast with mastitis will have a hot, tender, and usually red area. When you touch this area, it'll hurt a lot. You'll be able to feel a lump or several little ones inside the tender area of your breast.
Mastitis occurs when milk stays stagnant in the breast.
This usually happens when you have a plugged milk duct. The milk in the reservoir connected in this duct stays in the breast. Bacteria enter through the nipple and cause an infection. The white spot is where one of the openings of the nipple is. When you finish nursing, pumping, or expressing, you notice that a part of your breast still feels full.