How do you express "watching your nephew grow up" in Korean?

Hello! It's been a little over a year since I came to Korea, and I'm living in Itaewon with my nephew. Recently, my nephew has been growing so fast, and I want to naturally say in Korean, "You've really grown a lot!" but I'm not sure how to express it exactly. I tried saying, "You've grown taller!" but it felt a bit awkward. Would something like "You're getting bigger" be more appropriate? Living in Korea is really enjoyable, but understanding the subtle nuances of the language is not easy. For those who are fluent in Korean, could you recommend expressions that can be used naturally in a similar situation? I would really appreciate your help!