Apply another layer of liner. Use either the pencil or the dark lipstick. If it’s lipstick, apply it using a brush not to step out of the original line. Keep cotton swabs at hand in case of making mistakes. Correct it at once instead of painting over it.
Add some glossy finish if you wish. Surely, if you have the best matte black lipstick, you might wish to skip this step. But if you don’t, the glossy effect might come in handy. Just add little lip gloss to the center of the lips. Next, purse the lips and then spread that gloss all over.