I'm not sure, but try checking information regarding your Montgomery Gland. I believe this is the "bumps" on your areola, responsible for cleaning your nipple. Maybe this is it. Maybe it's an infection of that gland.
Dear bamak: There are several possible explanations for the lump that you feel. However, without examination, it is impossible to speculate on this particular lump. As a rule of thumb, any new lump needs investigation. You should have your doctor do an examination and hopefully, he/she can shed some light on this for you.