You could get the lump removed if it is causing pressure symptoms, pain or you feeling uneasy about it. A benign lump is otherwise managed conservatively, with regular breast self exams and periodic follow ups with your physician.
About the reduced growth - it is not common for a benign lump to slow the normal growth of the breast tissue ; but in some cases the fibrosis associated with a lump could cause a reduction in the breast size. You need to discuss this with your doctor, because nothing can be said with a clinical examination.
Do tell us know about what your doctor says.
Hope this helps.
Did you notice any changes (increase in size, tenderness) in the breast lump? The breast lump could be a fibroadenoma and is a benign condition. What you should do is continue to be vigilant in observing any changes.
There are women who have asymmetrical breast. The lump will not prevent its growth. Sometimes, the handedness of the person affects the breast size (say a right-handed person will notice a slightly bigger right breast relative to the left). This could be due to the more developed muscle on the right side.
Hope that helped.