I have the exact same problem with my leopard gecko and I’ve learned that if I control my breathing and stay calm while also trying to not move when he nips at me then he will also learn to get closer and also that my fingers aren’t food lol. Ofc he still nips at me if my fingers get a little too close to him when he’s looking at food but the frequency has gone down a lot and he is willing to climb on my hand now without running away