Just place a towel (not too thick) over the bump and take a board and a hammer and hit it. The towel stops it from marring furniture and start light then harder till it goes down. First you have to take out the long screw you put in and even if you put in a fatter screw make it shorter, or none of it will work.
If you want to keep things really easy, cover the spot with a towel to prevent further marks and lightly hammer over your bump with a rubber mallet, not a hammer. Most of the time, you can get the bump almost level with the surrounding wood without any further damage.
I would take out the "bump" and clean all the area around the hole with a brush or whatever to get rid of the dust, etc. Then put wood glue on the piece and the area of the hole. Then put together. If you can clamp it, then do that, if not place something heavy on top to keep the pieces together until they dry.
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