I would hammer it flat, get a dremel in there and put a nice bevel on it, if you have to pound flat again, then weld it shut, then put a plate on it. Only if it is not affecting the geometry on front end, if it affecting front end,straightened the problem area then weld and reinforce
Is that not affecting the stength and integrity of the spring hanger? i'm not too familiar with how these trucks look when stock, so i'm not sure what i'm really looking at here.
my first thought was to plate it, i have a plasma cutter so i can make a nice plate to cover and reinforce the area.
i'm not too worried about alignment, because it's a trail only truck.