If it's a minor dent with no damage to the paint a mobile dent repair service should be able to help. If it's creased or torn the metal it will need a more extensive repair at a bodyshop.

The most expensive part of the work is likely to be repainting the panel (or a section of it) to match the rest of the car, particularly if it's a metallic colour.

If you have a question about cars, send it to me and I'll do my best to answer it.