bugaboo

nouns

an imaginary monster used to frighten children
bogeyman, booger, boogeyman, bugaboo, bugbear
a source of concern
"the old bugaboo of inflation still bothers them"
bugaboo
is a type of (narrower)
something or someone that causes anxiety; a source of unhappiness
"New York traffic is a constant concern"; "it's a major worry"
concern, headache, vexation, worry