So, when you drill plastic, some of it melts, and sticks to the larger piece. It should snap off very easily. Yes, a vendor should have cleaned that up before you got it.... but... c'mon. Push a nail through that hole and it'll be fine.
Also, how exactly are you ill equipped for trimming control panel artwork? Mount the artwork and run a knife around the edges of your control panel. And, yes, that's how all control panel artwork is done.