( especially BrE ) to not spend time / effort on sth, because it is not important or you are not interested in it
NOT BOTHER YOURSELF / YOUR HEAD WITH / ABOUT STH
Meaning of NOT BOTHER YOURSELF / YOUR HEAD WITH / ABOUT STH in English
Oxford Advanced Learner's English Dictionary. Оксфордский английский словарь для изучающик язык на продвинутом уровне. 2005