I guess you've wrote the verb ending -니, because 보니 consists of "보다(verb: see)" + -니. the ending -니 is used to indicate the causal relationship between the actions.
밥을 먹으"니" 배가 부르다. (You're stuffed. Why? Because you've eaten something.)
비가 오"니" 땅이 젖는다.
너를 보니 예전 친구가 생각이 난다.