An idiom meaning that old feelings or conflicts flare up again; often used when former romantic feelings are rekindled (literally, 'the burned stake catches fire').
偶然再会したら、昔の気持ちが蘇り焼けぼっくいに火がついてしまった。
When we ran into each other by chance, old feelings came back and the embers flared up again.
別れてから何年も経っているのに、たまに話すと焼けぼっくいに火がつくことがある。
Even after years apart, sometimes talking rekindles old flames.
SNSで過去の出来事が蒸し返され、関係者の間で焼けぼっくいに火がついたようだ。
An old issue was brought up on social media, and it seems to have reignited tensions among those involved.