If this was an insurance repair, contact your insurance company. They have policies for when additional repairs are needed afterwards. Tell them it’s something you noticed later. And if it’s anything that could plausibly be related to the accident, they should cover it. It’s possible there is still concealed damage that is putting stress on the light causing it to separate and let moisture in. If your insurance company OKs it, I would let a different body shop handle the repair and check out the previous work.

If you paid out of pocket, you’re probably out of luck at this point.