Its a few days before my period & i found a painful lump in my breast. is it safe to wait & see if the lump leaves after my period? im a 21 year old.

Yes: Most lumps or nodules that young women your age find are areas of normal breast tissue which can become more prominent just before a period. They are most likely benign cysts (fibrocystic disease) or fibroadenomas. They are not diseases but actually normal. As you say, if the lump persists after your period or if you have any concern with this lump, it would be wise to visit your doctor.