I did something similar, hung the bumper end on a post in my driveway. A mallet won't do it. A friend and I straightened it with a couple of deformable blocks in a small hydraulic press. The bumper comes off with two screws into the frame on each side. Pull it and take it to a body shop if you don't have access to a small press.
"You cannot reason someone out of a position they have not been reasoned into"
Al, K5TAN and Missy, N4RGO
2002 Classic 30 Slideout
2001 Safari 25 RB Twin (Gone, but not forgotten)
2013 Dodge 2500 Laramie 4x4 Megacab Cummins
WBCCI 1322, TAC FL-39, AIR 82265