One point is that repair, filling in with touch-up paint, is what I would recommend.
A total repaint is not only expensive but I have almost never seen any repaint that won't chip a lOT worse than factory paint, even if they use the right flex agent and are a good shop. Factory paint is just more durable.
I would be sure to clean the area well, try to rough up the bottom of the scratch and use a good wax remover. I offer products by Wurth, and Wurth Clean Solve is used by many shops for paint prep. Most paint supply stores will also sell you a quart of wax remover/paint prep.
The touch up won't be as durable as original paint, but at least on the bumper you don't have to worry about rust.
The way I work on these is to lightly rough up the bottom of the scratch with 1000 grit wet sandpaper. Also try to smooth any edges on the scratch and remove any loose paint.
Clean and dry.
Start with the color paint, and lay it inside the chip by thin layers. You will have to buy some thinner to go with the paint as almost all touch-up paint is way too thick.
Have patience and work in thin layers, giving them plenty of time to dry between coats. As you get to almost level with the original paint, start in with clearcoat. Put this in till it is higher than the surrounding paint.
Then lightly sand (let the paint cure for a couple of days at least) with some 1500 to 2000 grit staying as close to ON the new paint as possible.
it is really tough to get shine back once you take it off, so I would not sand the surrounding area at all other than what just is necessary to level the paint.
Finish with a good glaze and wax.