If you want to do the patina thing w/ brass black, or cold blue but the dent in the brass still bothers you,,,you can fill the dent first with common lead/tin soft solder using a small electric soldering tip or elec soldering gun. Done with the part still in the wood so you don't have to pull it out risking damaging it.
Just clean the dent area, a tiny bit of flux, then tin the soldering tip and hold it aginst the area for a moment and it'll quickly flow onto the brass. Add a bit more solder if needed and you're done. Clear it off down smooth and level with the surrounding brass.
Then use (soft) solder black to color the solder and blend it with the coloring of the brass around it done with brass-black and or cold blue.
Don't use the newer lead-free Silver Soft Solder for this as the solder black won't color it much if at all. It'll remain a bright white color,,which for a tiny area might do OK too if the surrounding brass isn't tarnished. The two blend fairly well to the eye when bright, but the brass will eventually tarnish and then the Silver Soft Solder patch will show for sure.
Plain old 60/40 or 50/50 lead/tin solder works good.,,and no you won't damage the wood doing this with a soldering gun. It'll take but a few moments to actually solder the dent up.
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Another way would be to drill a small hole right through the dent,,then bevel countersink it to the edge of the dent. Make a 'tack' out of brass wire/rod,you'll have to mushroom the head of the tack and form it to the countersink you cut.
Then put a point on the tack and a few barbs on the post to keep it from backing out once hammered in.
CArefully hammer it into place,,you may need to drill a slightly undersize guide hole for it in a hardwood stock. The head driven down to just seat in the countersink you cut. Then face off the excess brass tack. It should cover and fill the dent area and blend in with the surrounding brass plate. Don't hammer it in too far or you'll create another dent around the tack head!
These are a couple ways I'd consider if I couldn't or didn't want to pull the plate out and pound the dent out to fix it.