I re-adjusted the clamps on the left side of the bumper to squeeze the bumper with the side panel as the part that was originally attached to the clamps had broke. The other option would be to weld something to the bumper so you don't have to force the clamps to hold the bumper to the side panel.

You can only do this if your bumper still has enough plastic for the clamp to hold on to. If it doesn't, you might have to either drill new holes, or get a thin metal plate to be squeezed between the bumper and the clamp.