So when you cut the panel, the gap created from the cut probably expanded a bit more than the thickness of the blade used and that allowed the panel to go back into place.
If this is the case, its telling you that you need to planish, (hammer and dolly) the weld to stretch it out some.
The metal at the weld has shrunk causing the distortion further away.
Do not tap the metal at the warped area. As you slowly planish the weld, you will see the problem disappear.