His wiping is invalidated, then he looks: If he is not in a state of ritual impurity, then he does not have to perform ablution, and it suffices for him to wash his feet only, without washing the rest of the limbs. As for if he is in a state of ritual impurity, then he must perform ablution; this is because the exit of the foot is not a nullifier in reality, but rather the nullifier is the previous state of impurity. However, when his foot exited, the effect of the impurity appeared on the foot. Refer to: Al-Maraqī page 134, and Sharh Al-Wiqayah page 117, and Allah knows best.