Many women with breast cysts are helped by cutting down on caffeine in their diet, and also by using supplements such as Vit. E, or evening primrose oil capsules. (?)
This sounds too simple but it really makes a huge difference for many,
No, you should not be worried, at least not about cancer, as breast cancer does not present itself in the way you mention.
There are different kind of lumps and most often, especially in younger people, those are cysts (fluid filled), or fibroadenomas (solid) There are benign , or non cancerous.
Sometimes they hurt, and they often get worse before your period and then ease up. They can hurt and be very annoying but usually no surgery is done on them unless there is really a big problem associated with the condition or the doctors are unsure. but with yours that is not the case.
Best, Katrin