Regardless where the fat is injected, hard lumps should not occur. Usually fat has a chance to live when small amounts are delivered into a well vascularized space (enough blood circulation to create a neighborhood of oxygen-rich cells to make the new cells survive). If however, there is a large amount in one area, the center of the fat mass may die as oxygen can't travel the distance through all these new cells from the outside of the mass. Cysts can occasionally form but delayed infections can also develop. Hematomas are blood collections and they may solidify after a while. These can get infected and even calcify after many months. You should be seen by your surgeon for an evaluation.