You sure that it's not the outside of the plastic melted by protectant or cleaner? It doesn't look like it's on the inside to me. I doubt the plastic lens is very expensive. The cluster is very easy to remove. Push the top cover towards the front of the car. It will pop off and expose the screws that hold it to the dash. There's only a couple of electrical plugs to remove before the cluster pops out. The lenses are usually pretty easy to take off after removing several screws.
I think it's on the inside, but now that you say that I'm not sure. I can't figure out how to push the top cover off the panel. I always think I'm pushing too hard. And if they're not inside, I can't find any replacement plastic lenses.
If the plastic is damaged, you could try some Novus plastic polish. It comes in three grits. You start with 3 to remove the damage, then go to 2 to clean it up, and the finish with 1 to polish it. I have used in on a lot of plastic pieces and it has always worked great for me.