Recently did the exact thing on my friends fietsa bumper after someone hit the bit we'd painted with a shopping trolley....
Sand it back so its smooth, something like 800, 1200 should do, the mask up a small square around the area, give it quite a few layers of high build primer every 20 mins or so, so it basically fills the dent, remove all tape and leave to harden for a day or so.
Now sand this back until you start to see the paint around the dent again, and it becomes nice and flat around the edges (so you can no longer feel the square outline from masking with you eyes closed)
Now your dent should basically be full of primer, level with your current paint job, after this, sand lightly around the area you've primiered, i.e a bit further out onto the good paint.... to key it with a 1500 or somehting.
Now get your paint and spray from quite a distance at angles so that you cover your chip but overspray onto your now keyed paint work, repeat until its invisible, leave to harden and the laquer in the same manor.
Sorry for the essay