rear one's head

verb2

1. •
   To raise one's head.
2. •
   To appear and cause problems or stress, especially at an inopportune time (said of something or [rare] someone that is undesirable or unwelcome).

   • One problem that reared its head in 1983 would prove more difficult to solve, with the heat that summer leading to a number of engine failures. — 2021