Can I use the word "report" only on the official occasion?
Yes, I would say that the word "report" is a pretty formal word. You will not usually hear native English speakers use it outside of a formal or polite situation. In more casual conversation it would be better to use "reporting words" such as "tell" and "say". Ex: I will report to the teacher. Ex: I will tell the teacher. Ex: What did he report to you? Ex: What did he say to you?