I broke a component on my Arduino while trying to hold a nut with pliers ( because a key does not fit in there! ).

I circled it in red in the attachment. It looks like a component that is right after the power jack. It looks like a capacitor or resistor, not sure.

 

I'll volunteer a guess. It might be a polyfuse. It looks like a resistor based on the color. How do you know that it is broken?

 

The schematics can be found here:
https://docs.arduino.cc/hardware/due/

 

From MrChips link (above), it looks like an SMD inductor.

 

Thanks for the schematic.
I found the component on DigiKey, it's a FERRITE BEAD 30 OHM:
https://www.digikey.ca/en/products/detail/bourns-inc/mh2029-300y/2563323
I think I can just solder a wire in it's place as a quick fix, or I can just power the board with USB or Vin pin instead

 

Ferrite bead would be for noise suppression, there's likely no harm in shorting it, but no guarantee it will work. I would give it a try. That one is only 30 ohm at 100MHz, at DC it's 25 mOhm (mili).

 

If you have a small ferrite bead, non-surface mount type, and if you have some fairly decent soldering ability, you can build a nonsurface mount ferrite bead and solder it on above the board in the same area. It might even block noise better.