Breast Cancer is rarely associated with breast pain. You don't mention your age and this may well be a factor ... Fibrocystic Breast Condition occurs in about 50% of women. This can cause breast tenderness and the formation of cysts due to the hormone levels in the body. If you are terribly concerned about this I would advise you to see you Physician for a clinical breast exam. Regards ....
You need to see your doctor and get a referral to your breast clinic for tests. It might not be anything to worry about but sooner rather than later is my motto and if there is anything to worry about then that's even more relevant.
Good luck.