The son fell in love, but I don't know what to do

 

My son is 10 years old and he fell in love for the first time. But not a peer, but a girl who is 5 years old. The girl is very beautiful, she lives in our yard and runs with her friends, but she is a child, and my son is already a teenager. He does not take his eyes off her. Follows her heels. He does not sleep at night, and keeps telling me about her. How she looked at him, how she walks with her friends, describes her as a princess from a fairy tale. I am very worried and do not know if it is worth contacting a psychologist with him. After all, this is not normal. He has friends and girl classmates. He walks with them and communicates and in general he is the soul of the company. But as soon as this girl appears in the yard, then that's it. He leaves his friends and sits down on the bench alone and looks after her. This girl is quite a child and I am trying to explain to him, but he does not listen. He runs to buy her some sweets with his pocket money. Her parents told me about it, but they said with a laugh that, they say, children, and already in love. But my son is already a teenager. It seems strange to me. Do I need to take him to a psychologist or psychiatrist? Maybe someone had cases? I am very worried about him. It's not right. He writes her letters of love and puts them in the nightstand there is already a whole pile. What to do?