Here's why Din Djarin let Baby Yoda touch his face in more characters and elements from the larger Star Wars universe, Din and Baby Yoda's dynamic was the beating heart of the series.
In The Mandalorian season 2, Din embarks on a mission to reunite Baby Yoda with the Jedi, so the child can receive proper training and master his Force abilities. This quest culminated with Grogu leaving with Luke Skywalker, who had sensed the child's presence when the youngster called out to the Force on Tython. But before Baby Yoda started his new journey as a Jedi in training (again), he said goodbye to Din in a very emotional scene. The farewell between The Mandalorian's two stars was a major development, illustrating how much Din has grown since the first episode.
As Din is about to send Grogu off with Luke, the child places his hand on Din's trademark helmet. Din then removes the helmet so Baby Yoda can see his face for the first time. The infant's hand rests on Din's face before he walks over to Luke and starts the next chapter of his life. For Din, this was a very significant moment, as it presumably is the first time someone has touched his face since he was a child himself.
This is the latest example of Pedro Pascal's performance to truly shine.
Beyond Din's helmet rule, the touching sequence served as an illustration of the strong bond he has with Baby Yoda. After all the pair has been through together, they are family. Over the course of the first two seasons, they've developed a father/son dynamic that was The Mandalorian's emotional core. That Baby Yoda was able to touch Din's face makes their goodbye that much more impactful than it would have been if he just saw the face. The physical adds another layer to their connection, showing that even though they're separated (for now, anyway), they'll always be together in spirit. It's apparent the two have a deep love for one another, making Grogu's farewell one of the most poignant scenes in Star Wars.