You need 1) a breast ultrasound and 2) a diagnostic mammogram if you haven't had one within the last 6 months, assuming you're over 35-40. (If you're younger than 35, you may not need a mammogram.) If they're both negative, and your doctor still thinks it's nothing, waiting 3 months is not a bad idea. If US and mammogram are both negative, and you're still worried, you can get a second opinion from a surgeon. If she feels a significant lump, she can do a biopsy, but if she doesn't feel a significant lump, she will not do a biopsy. Good luck!