France· medium· informal
avoir les chevilles qui enflent
“to have swelling ankles”
Meaning
to become full of oneself after a small success
Explanation
For someone who's let one small win go straight to their head, acting far more important than the moment really calls for.
Example
Depuis qu'il a gagné ce petit concours, il a les chevilles qui enflent.
Ever since he won that little competition, he's been acting very self-important.
Origin
Origin uncertain.