to suppress one's pain, grief etc (and preserve self-control under trying circumstances): стиснув зубы - gritting one's teeth.
Сапоги примёрзли. Абуталип морщился, стиснув зубы, стонал, когда все дружно пытались стащить их с ног (Айтматов 2). The boots were frozen on his feet. Abutalip frowned, gritting his teeth and groaning when everyone tried to take them off (2a).