You may decide to stop here and replace the assembly altogether. However, you may otherwise decide to separate the lens from the plastic enclosure.

In this case, there is a notch that is part of the lens shape (green) that fits into a matching groove in the enclosure (red). You will need to employ leverage to push the lens notch in and down while pulling the wall of the enclosure up in order to remove the lens.

WARNING: Removing the lens by exerting force on both it and the enclosure is very likely to break the fragile enclosure to some degree. The tolerances are very tight and the enclosure is reinforced in many different locations that may make the lens removal extremely difficult. Be very careful and think twice before attempting to remove the lens.