Which sentence uses fester correctly?

The fester of work that she still had to complete was daunting.
The , fester, of work that she still had to complete was daunting.

The sky was beginning to fester as the rain clouds rolled in.
The sky was beginning to , fester, as the rain clouds rolled in.

Do not fester your big brother while he is trying to complete his homework.
Do not , fester, your big brother while he is trying to complete his homework.

He needs medical attention right away so the wound does not fester.