撕扯着嘴边de微笑掩饰着心中de疼痛
[sī chĕ zhe zuĭ biān de wēi xiào yăn shì zhe xīn zhōng de téng tòng]
It means forcing a smile while masking the pain in the heart. A metaphorical way of describing internal suffering hidden by outward appearances or a facade of happiness.