The meaning of words can be inferred from context. For example, in his book Elantris, Brandon Sanderson has a character insert words from his (fictional) mother-tongue into conversation.
Raoden breathed a sigh of relief. "Whoever you are, I'm glad to see you. I was beginning to think everyone in here was either dying or insane."
"We can't be dying," the man responded with a snort. "We're already dead. Kolo?"
(Brandon Sanderson, Elantris, chapter 1)
We can infer that 'kolo?' means something along the lines of 'understand?'
Most commonly, I have seen such inserts used for curses, exclamations of extreme surprise, or alternatively - endearments. (For examples of the last, you might be familiar with 'imzadi' ('bloved') from Star Trek, or you might remember how Gomez Addams calls Morticia "Cara mia"). What all those usages have in common is that the tone implied from the conversation (or sounded, in the case of film) is sufficient to convey meaning, and is more important than the exact meaning. However, I have deliberately brought above an example that is a bit more complex, and yet easily understood, to show how you don't need to limit yourself to exclamations and endearments.
Inserts of particular foreign words into a character's conversation can be, and often are used as, a recognisable "verbal tic".
One important note: you can't use a Chinese character to represent a word - if you're writing in English, you've got to use transliteration. The Chinese squiggly makes no sound in my mind, it's a blank. I can't tell one character from another. In another similar discussion on this site, someone compared Chinese characters to squished spiders; the fact that I couldn't tell a squashed spider from an actual Chinese character says something about me, and nothing about Chinese characters, but it is true. And, more importantly, it will be true of your readers, unless you're writing for a bilingual public only.
