Physical damage: a small scratch, chip, or nick on a surface or object. Often used in formal or written contexts.
This pottery has a chip.
Abstract imperfection: a moral flaw, character defect, or shortcoming. Often used in literary or formal criticism.
A stain on one's honor or reputation; a cause of shame. Rare and literary.
There is a flaw in his character.
That incident became a disgrace to his career.
欠点 is the standard word for a defect, fault, or shortcoming. かきん is rarer and carries a more classical, literary tone.
Rare kanji spelling; both characters are uncommon. The word is usually written in kana.
Alternate rare kanji spelling; 釁 is a very uncommon character.
The exact derivation is uncertain. The kanji 瑕 and 瑾/釁 are associated with flaws in jade and cracks in ritual vessels, respectively, suggesting a classical Chinese origin for the concept of a small imperfection.