My Yorkie Yelps When I Pick Him Up By His Abdomen Area?

[Mockingjay109]

He's 2 years old and today I tried picking him up to move put him in his kennel and he yelped I grabbed him from his ribcage gently as I could he didn't and has never done this before so the I grabbed him by his legs sort of hugging his legs but he's jumping and running fine nothing else is bothering him could this be a serious thing I'm going to take him to the vet just in case it's a one day thing but he's never done this he was outside by our pool with clean water in a bowl for most of the day because we where getting our house fixed.