to be extremely hardworking in one's studies; derived from the story of Su Qin who stabbed his thigh with an awl to stay awake while studying

(literary) to study with great diligence; refers to the idiom 头悬梁，锥刺股 tóu​xuán​liáng​zhuī​cì​gǔ where one ties their hair to a beam to prevent falling asleep