Solid mass in breast after surgery

We warn patients that a lump after surgery or biopsy is completely normal and temporary. It can be for one of two reasons: blood blister (hematoma) formation, or healthy tissue inflammation. Both conditions makes a tough slightly tender knot and both situations resolve over weeks to months, depending on how large they are. One month is still relatively early in the healing process. Give it more time and the hard area should melt. Very very rarely tissue inflammation leads to fat necrosis where fatty tissue can become permanently hardened like a smal pebble. But this takes much longer and wouldn't have happened in one month. 

Initially the area of the breast mass removed is filled with fluid.  As this dissipates scarring in the area develops.  If this is not the case and there is a new mass then a physical exam and other evaluations are necessary.  Most of the time an ultrasound would be used to investigate this further.