My breast feeding wife noticed an oblong shaped lump in her breast about 6 months ago which later disappear but reappear 3 weeks ago.do we wait or ?

OK to watch: If she is continuing to lactate, the previously blocked milk duct was likely the cause of the lump, which resolved as this one should. Sometimes moist heat, with continued feeding on the side of the "milk cyst" should help it to go down. If she develops redness, fever, or increasing tenderness, then infection has to be considered; antibiotics will be indicated.