Don't sweat it. You can fix this.

Let the Clear set up solid for a couple of days. Then sand the insert flat. I would mask off the insert with Frisket or if you must, blue or green masking tape to protect the surrounding playfield. You can use a piece of paint stirring stick for a sanding block. Sand it flat (or even a bit concave by sanding with a finger) and then re-open any bubbles that are not opened - do the xacto thing as Vid suggested. Wipe em with naptha and then flow (don't drop - set the tip of the eye dropper on the playfield and flow the clear gently into the clear) again. You'll fix this - don't worry. I don't think you sanded it quite enough the first time. I will often use 400 grit to take down something like that - but you have to be VERY careful not to sand through and damage the art work. Probably best to stick with the 800 for now and just sand them a bit longer.

This can be repaired so know one will ever tell this happened