心事 is read as しんじ (shinji) and means mind.
しんじ
shinji
かんしんじ
matter of concern
しんじゅう
double suicide
こころから
from the bottom of one's heart
しんり
state of mind
ここち
sensation of doing
こころづよい
heartening
しんりがく
psychology
しんちゅう
one's heart
こころ
the meaning of a phrase (riddle, etc.)
しん
Chinese "Heart" constellation (one of the 28 mansions)
こころいき
spirit
しんがい
unthinkable