oops, how do I fix this?

That’s what I would do is route the biscuit down about a 1/4” and find a good match of the grain and add a little glue and pound in let dry and trim and sand even.

-- https://www.artisticwoodstudio.com/videos wood crafting & woodworking classes

i’m three on that
hold your scraps
the same way the top is running
and see how best the grain will match
don’t hold it sideways to the work
and cut it that way too

-- david - only thru kindness can this world be whole . If we don't succeed we run the risk of failure. Dan Quayle

inlay a contrasting wood at some repeating pattern around the perimeter or a continuous groove filled with a band

You have nothing to loose. you fix,it works, great otherwise you redo.
If you don’t fix you redo anyway.

As for the router I have a word of caution:

It is a round edge and about only 3/4 if I see correctly. you need an adequate width(or depth) to ride that router base on even a palm router.
clampping a couple of pieces of strait wood to your piece for the router base will help.
Since the main piece is round and the router bit has a pre-determined “height” the groove will end up being arched.
You can bandsaw you corresponding plug and since the inside part will not be visible it does not have to be perfect. As for the end grain I agree with the above post.

I am pretty sure there is a better way for the routing.

-- Abbas, Castro Valley, CA

As for the repair, I couldn’t agree more with a1Jim. The routing can best be done with a slot cutting blade, IMHO. They scare the bejezzes out of me to run but the cut a groove parallel to the face the router base sits on. Good luck, you got some good advice in the above listings.

-- "Man's ingenuity has outrun his intelligence" (Joseph Wood Krutch)

Why not use your biscuit joiner to make the cutout? , you’d have better control easier than a router.

Paul M

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees. http://thecanadianschooloffrenchmarquetry.com/

Just another opinion for you to chew on…
I think your initial idea of using a chisel will work, and perhaps it will allow you to take your time and work slower. You’ll really be able to exercise the patience that woodworking often requires when you have to cover up mistakes so that few people will ever notice. IMO, that’s a unique art-form all on its own…hiding a mistake so that no one knows but you (and maybe some other woodworker with a very critical eye…LOL).

So go ahead with the chisel if you want. Use a small chisel if you have it, maybe 1/4” or even 1/8” wide will be good. Carefully make a shallow cut around the perimeter of the biscuit and begin removing the waste. As was already suggested, you only need to remove material about 1/4” deep.

Here’s where you can really fool everyone with a gorgeous repair:
Do you still have the scrap piece from when the curved shape of the drop-leaf was cut out? Locate a spot in the scrap JUST PAST WHERE THE BISCUIT LIES IN THE SCRAP PIECE. See if you can cut out an inlay piece using a bandsaw or jigsaw or scrollsaw or coping saw. Glue in the plug with a good CA glue and accelerator like Satellite City’s “Super T”, and sand or rout it flush. I don’t know if my explanation is clear, so I’ve drawn a little sketch in paint. Let me know if you need any more help. At the very least, I can help you make it worse!!! ;-D

-- Lane Custom Guitars and Basses

I have discounted the biscuit joiner because it leaves too little material on the end of the biscuit cut. I also thought that because of the rounded edge it might produce a shallow cut and not complete.
This said I have never tried a biscuit joiner on a round edge and it might be worth a try.
Of course on a scrap piece with the same radius.

-- Abbas, Castro Valley, CA