When 'lump" is mentioned here, no-one is referring to any simple protruberance of large man-boobs but, rather, a fatty but firm growth, distinct from the surrounding flesh, beneath the nipple or aereola.
As I mentioned above, if your nipples are inflated, distended or swollen then it could be an indication of inadequate AI dosing. If they're painful then you should ascertain the cause of the pain and feel for lumps. Itching could also be a sign of insufficient AI but, again, isn't necessarily so.