What does "put you on the spot" mean?
This is an informal expression. When someone is "put on the spot," it means that they are being forced into a difficult situation or asked a question that is difficult or awkward to answer. In this case, Jimmy Fallon says "I don't want to put you on the spot" to show that he doesn't want to pressure Ariana Grande to accept his request, especially as the situation could turn awkward if she refuses to sing. Ex: Jimmy put Ariana on the spot when he asked her to sing in front of hundreds of people. Ex: Jacky was put on the spot because of her boyfriend's public proposal.