First, welcome to the bite club. The anticipation or fear of a bite is almost always worse than the bite itself.
Secondly, I agree, it was just too much too soon for him. He's tiny and not used to handling. That means he will get scared very easily. Slow down. Shorter, less hectic handling sessions for a while. Build trust.
Also, in your response (above), you nailed it. He was "getting pretty squirmy." He warned you and told you, ENOUGH! You didn't listen.
I've never been bitten by my BP Shayna, but I know when she's done with handling. Usually 10-15 minutes in (tops) she starts getting really active. If I don't listen and put her back, she gets stressed; a little more darty and can even breath heavier.
As you learn to get to know Phantom, and vice versa, you will learn to read him better.
He sounds pretty chill otherwise, especially for not being handled much, and will 99% grow out of this stage with continued gentle handling and with size.
I wouldn't worry about ruining the bonding. It's an isolated incident. He won't hold it against you. Learn and move on.
Were your kids and/or wife freaked out?
Also, good you didn't immediately throw him back in his tank. You don't want to reinforce that he gets what he wants if he bites. It was probably a minute later, which is plenty of time for him to not make a connection.