Front signal lights wobble in their housing.

The front turn signal lights stay in the bumper okay, but if you touch them, they wobble around and push inward, but don't fall out. What part is missing from it to cause that? I also have an issue with my front bumper wobbling on the drivers side. The nut is missing in order to hold it on correctly, but am unsure of what size nut it takes to keep it held in place.