The worst that will happen is you will loose your good condition bonus £600 and wouldn’t affect your insurance as you wouldn’t be making a claim. However Ive heard of cars going back with all manner of dents and scratches and still got their £600 GCB
Now if your able to source a new light for under £200 and get it fitted you wouldn’t take a massive hit if you were to loose your GCB.
Can you post a picture of the damage rather than advising you blind, or my advice is ask the question here as well include a picture if you can of the damage here as I think you will get a more reply’s.
https://forum.whichmobilitycar.co.uk/forums/topic/motability-question-we-can-answer-it/