I've came up with a lump inside my breast and in worried, i'm not sure what it is?

Have it checked up: Lumps in breast can be real or a false alarm if examined improperly. So I would ask you to have it confirmed by another person even a friend or family member. If there is agreement that the lump is real then go see your doctor for confirmation. It is unlikely to have cancer under 20 years of age but benign tumors such as Fibroadenoma do occur in young girls but these are entirely benign.

The probability: is overwhelming, at your age, that whatever you are feeling is benign. However, if you are concerned, you can have your doc check it out. It might help alleviate your worries.