This one comes from the sports world. Here’s the full context: “Sunday’s Bills-Jaguars game started off tense when Jalen Ramsey took time from his busy day to remind Buffalo’s players they were trash. That conflict boiled to a head in the third quarter when a brawl erupted on the turf at New Era Field.” Here’s the citation: https://www.sbnation.com/2018/11/25/18111422/jaguars-bills-fight-leonard-fournette-shaq-lawson.
This is a nice conflation of “boiled over” (to become extremely intense or out of control) and “come to a head” (to reach a point of intensity at which action must be taken). “Come to a boil” (to reach a crucial point) is also probably in the mix considering the context. A boil on the skin has a “head” of sorts and so could have been in the writer’s mind. A big thanks to Barry Eigen for spotting this one!