Yan Fei's purpose of entering Dinosaur Island is quite simple.
First, he wants to prepare some meat to eat, and second, he's considering whether or not to explore other islands.
There's now only one big island in this area that he hasn't stepped foot on yet. Exploring it would be simple: he just needs to find a chance to fly over, find a safe spot to land, and explore it slowly in the future.
The reason he didn't explore before boils down to habitual laziness. The dinosaur world has always been visible to him since he was a child, and so he took it for granted, much like how one takes for granted the bed they sleep in and the blanket they use. He only thinks of those when he's sleepy and lazy, otherwise, he basically ignores them.
Anyway, the whole world is his own and he can come and go whenever he wants. Sometimes he feels curious, but most of the time, he is too busy in the real world to care.
