Depending where it is, then one of the PDR ( Paintless Dent Removal ) companies such as Dent Wizard, or Dent Master, etc, etc may be able to get the dent out.
To do so, they need to be able to get in at the back of the dent, they then use metal rods, with rubber ends to push the dent out.
Doesn't sound as if it would be much good, but I had one just above the rear arch that you can no longer see.
Note that they don't do any painting ( as the P in PDR implies )
Gus