To exaggerate trivial matters into something much bigger; making a mountain out of a molehill (four-character idiom).
彼はいつも些細なミスを針小棒大に騒ぐので、雰囲気が悪くなる。
He always makes a huge fuss over small mistakes, which ruins the atmosphere.
新聞の見出しが針小棒大で、記事を読むと実際は大したことではなかった。
The newspaper headline was sensationalized; when you read the article it wasn't actually a big deal.
針小棒大を避けて、冷静に事実を確認しよう。
Avoid exaggeration; let's calmly check the facts.