If your mammogram report stated that the imagery seen was normal,then a BIRADS score of 2 or 3 must have been added in your report.Many women have benign lumps, like cysts or fibroadnomas and these lumps can be quite painful, especially during the menstrual cycles.You can surely ask your doctor to order an Ultra sound test to assure you if this lump is a cyst,which is a fluid filled sac.Cysts can be aspirated by a fine needle if you feel a lot on pain or if the cysts is quite large.Fibroadenoma is a solid lump and also it can be removed if you feel too much pain or becomes too large.If I were you I wouldn't wait one year and worry needlessly for that long, especially if you BIRADS score is a 3.Also try to avoid caffeine and your salt intake,it will help lessen the pain Best wishes...
Was there any reaction/ recommendation made by the doctor when the lump was felt?
You might want to contact the doctor and express your concern. Ask if this lump requires further investigation like, a follow-up diagnostic test. Personally, I think that a year is too long to wait and wonder about about the nature of this growth.