A lump was found under the wound 12 days after breast fibroma operation. Why? Not cut clean, or is there something wrong with the wound?

I just made it yesterday. The doctor told me this problem in advance and told me not to worry. Because you removed the tumor and a part of the tissue, damaged a part of the capillaries, and the blood did not flow in the past, leaving a lump at the place where you operated, which is simply hematocele. Generally, it can be completely absorbed after three months, and then you can go to the hospital for re-examination. I just read the question about this question for a long time and found that there is no such answer. Let's trust the doctor. I wish you a speedy recovery ~