Breast dimple :/

Hello ladies i need some help fast! I am only 17 and have small breasts, 12 B and when i push my breasts together i get two large lines/dimples on the insides of my breasts where i am trying to push them together. Could this be cancer? i also have a large lump in my left breast that i have had for a few years which i think is a cyst. although i’m worried as i have carried my phone in that breast pocket at school for a few years. YES i will go to a doctor but in the mean time i need some advice.