You could get them plastic welded. But that is the most expensive option. Sgould's suggestion of a large washer is the way to go, covering it up entirely. Glue-ing the washer would work with a slow set epoxy. I think nearly every 9-5 would have this issue too. underneath the hole there is no real support for the bracket, so it will happen again if you don't remedy that side of things.
Is the headlamp loose in its cavity? If not then is is really only cosmetic and only you know. Apart from everyone on this forum....