。
Tears streamed down my cheeks.
Literal
Tears [subject-が] my [of-の] cheeks [object-を] flowed-down.
A first-person framing: 私の頬を流れ落ちた ('flowed down my cheeks'), with the compound verb 流れ落ちる ('flow + fall'). The を-marking of 頬 as path of motion remains standard.