godan verb (-ru), intransitive verb
swell up; become swollen
Describes a body part or area becoming visibly and often painfully swollen, typically due to injury, inflammation, or an allergic reaction.
虫に刺されて、腕が腫れ上がった。
My arm swelled up after being bitten by an insect.
転んだら、ひざがひどく腫れ上
When I fell, my knee swelled up badly.