If it goes away completely before it comes back, then it is not likely to be breast cancer related. It could be some sort of clogged or infected duct. If there is no redness or other sign of infection, you could wait until your next scheduled doctor's appointment to mention it. If it is getting worse or looks infected, go ahead and schedule an appointment to have the doctor check it out.
but it comes often whenever I change environment...... as at now it quite painful expecially when it comes in contact with my bra or dress
"Quite painful" means call the doctor. Because this happens when you change environment, it may turn out to be some sort of allergy. I'm not a doctor, so I don't know all the possibilities. However, pain is a signal that there is something wrong that needs to be checked out. I hope the doctor gives you good news and treatment that relieves your symptoms.
thanks am really greatful...........