I in the same spot, someone backed into the back left corner of mine and took off. Truck is under 2 months old and it left a nice crease in the metal. One of my friends owns a body business and has contracts with Dent Wizard, they looked at it and said it could not be done with the normal dentless tools. Not sure what other options are out there but outside of replacing the bumper he told me it was not a simple fix.
2010 DC 5.7 4X4 TRD Slate Metallic
2004 Yamaha R6 Track
2010 Aprilia RSV4 Street
2009 Weekend Warrior SX18 Trailer
2010 YZ250F Moto