>>2219649You should have cut closer. If an outline remains, turn the figure into a mask, reduce and feather it inwards a little, then invert it. Now only the 'edge' pixels can be effected by your tools. Erase them.
Since you were already finished, I selected the border using the above technique, copied it to another layer, and set the duplicate to 'multiply' before re-merging. That darkens the outline. Multiple copies will turn it black.
Because you'd left a rather thick border, I thinned it by selecting, expanding, smoothing (4 pixels), and feathering before erasing. That thinned the outline and simultaneously eliminated a lot of the jaggies.