I have tiny black dots under breasts. they itch, when i squeeze nothing comes out, also if i run my hand over it, it feels lumpy. what could it be?

Black dots: breasts: Skin at any location can be pigmented, and from your description, if they are raised ("lumpy") they may be simple "moles" (nevi). You should see a health professional to confirm.

Could be cysts: Likely small cysts that can occur in areas of skin. Wax like material can build up and become like black plugs occaisionally can get infected. Best idea is to have someone look at them and see if they can offer you a plan to control and prevent infection. Pain, redness or rapid growth need immediate attention

Not sure: The possibilities are endless, from benign nevi (moles on your skin, essentially) to the more sinister (melanoma, though that is an unusual spot for it to appear). In between, there are other possibilities. You may want to get a skin biopsy of the area - a direct, but uncomfortable, way of getting an answer. Or you could talk to a dermatologist or your primary doc and may be get a different view.