What is a term for something unwanted but which cannot be ignored?
Solution 1:
Something which is obvious but which people deliberately avoid or try to ignore can be called the elephant in the room.
Solution 2:
You could refer to the issue as a Task, Burden, or Necessity. Or could use multiple terms such as saying, "The Mayor saw it as a burden which kept returning to eat up his time, however, the worried citizen knew it was a necessity to maintain the safety and security of their peaceful city."