Painful lump in breast! also late period! what can be wrong?

See below: Breast pain can be cyclic or noncyclic. Cyclic pain typically is worse before your menstrual cycle & usually is relieved at the time your period begins. Noncyclic pain can be associated with a benign nodule (fibroadenoma) or cyst. Breast infection such as mastitis can cause pain, usually happens during time of breast feeding. Breast lump can be normal changes, cyst, a fibroadenoma or a cancer.

Low risk: Fortunately without a strong family history cancer at your age is still rare (though not impossible). You mentioned the missed period, could you be pregnant? Breast masses that respond to hormones will enlarge and sometimes hurt when those hormones begin to flow.