I hav pimple like bump on my left breast n its bin there 4 3years I had no problem but 2day it was hurting n I waited n popped it. Is it breast cancer?

No. Some skin lesions on the breast can be cancer, but these usually happen to older patients and they have nothing to "pop". This is probably a small skin lesion, often called an inclusion cyst. They can get infected or irritated. It may come back but a surgeon can easily remove it if it does.
No. It may have been a benign growth called a sebaceous cyst. Just watch and make sure it doesn't get infected from your treatment and you will be fine.