If part of your body puffs up, it becomes bigger because it is infected or injured.

My leg puffed up all around the insect bite. 我腿上被昆虫叮咬的部位肿了起来。

to become larger or full of air, or to make something become larger in this way

When the crust is golden and puffed up, take the pie out of the oven. 当外面的酥皮变成金黄色并鼓起来时，把馅饼从烤箱拿出来。