About A Month Ago I Fell Going Up The Stairs

About a month ago I fell going up the stairs and hit my shin against a stair very hard. There is some localized pain and a slight bruise but not as bad as it was when it first occurred. However, my concern now is that I feel a hard lump under the skin, about the size of a marble and there is pain and tenderness at the sight of the injury. Is this normal?