Depending on the lighting you can actually see an unnatural protrusion. That and the angle of his nose tip are highly indicative of the presence of a nose implant.
When you fill your cheeks with air (try it for yourself and see), the tip of your nose will become more pointed. In this picture you can see the protrusion becomes a lot more obvious.

Whether or not he got fillers/rhinoplasty, I personally think he is the most talented and attractive person in the universe. His nose in the pictures below was already wonderful so he is clearly a natural 100/10 cutie.

(Pre-debut pics. The last two are from his days training in LA in 2012. Sorry for the low res)

So this is my answer to the question based on my observations.

Saying someone may have gotten work done is not a way to discredit them, on the contrary, refusing to even speculate they may have done something is toxic because you may be denying the struggles&truths of many idols and unwillingly shaming those who did. Please take my conclusion on this matter with a grain of salt as these are only speculations, but I think it’s important to bring these things to light and have a mature and respectful conversation in order to fully love our idols and ourselves in a healthy way.✨

Source: He’s my absolute ultimate bias and 50% of my day is usually spent on something Jk-related.

Edit: there’s one individual in the comments section who needs to chill lol. Please interact with people respectfully and be mindful of other people’s mental health. No one has ever threatened me or sworn at me so much in my entire life. Also, spreading so much hate cannot be good for you either. Please take care of your mental health honey 💜 have a purple heart.