lance the boil

lance the boil

take decisive action to put an end to an undesirable situation.
The underlying image is of a boil being cut open with a lancet or other sharp surgical instrument, to release its pus.
2003 Yorkshire Post Today Mr Conway … said…it was time for Mr Duncan Smith to ‘lance the boil’ in his leadership. ‘There's a growing feeling of “it's got to end”.’
See also: boil, lance