the new kid on the block idiom informal
刚上路的新手，初来乍到者
someone who is new in a place or organization and has many things to learn about it
Realizing I was the new kid on the block in this job, I was determined to prove myself. 意识到自己在这份工作上还是个新手之后，我下定决心要证明自己的能力。