It's not just pride dooming Thor here, it's impatience. He'd reacted too quickly, too eager to swoop in and take this from Bucky without considering the risk of meddling like so.

Though Bucky is powerful, the punch isn't quite enough to wind Thor properly. The kick, however, is enough to sway him. He stumbles, but he uses his weight to try jerk Bucky down with him by pulling him around with the arm he has a hold of. It isn't enough force to rip it off if Bucky moves with the motion of it.

Carlos, you are terribly important to him, but he needs to take the kids to school.