assembled a new piece of furniture this weekend but can’t finish it because the holes in the legs were made incorrectly 

feels bad man

If you need to expand those holes, it should be rather simple to fit the drill bit size in the top holes and then you can open up the bottom two. 

You can also mark the bit with tape at the right depth in the top holes

If you need to shrink the two bottom holes on the left… maybe there is an adapter, or you can glue a chunk of dowel in there and drill small holes

Aspiring mad scientist,
support team @ /rainbow

Oh, is the piece upside down? A replacement might be easier then!