钻心

to sneak in / to infiltrate / to be piercingly painful / to be unbearable (of pain, itch etc)

variant of 鑽|钻[zuan4]

to drill / to bore / to get into / to make one's way into / to enter (a hole) / to thread one's way through / to study intensively / to dig into / to curry favor for personal gain

an auger / diamond

heart / mind / intention / center / core / CL:顆|颗[ke1],個|个[ge4]