I was removing my door panel to try to get some dents out of my door and I accidentally punched a small hole in the plastic material inside about the size of a dime. I put a piece of duct tape on both sides, but I am wondering should I be worried about mold or any kind of water damage in the door now?
No…
Don’t sweat it
The gray duct tape is probably the same color as the door panel, correct?
We have several S10 trucks in our fleet, and the interior is gray for every single one of them.
Well it wasn’t in the door panel but yes a gray door panel. I was referring the almost garbage bag looking material inside the door panel. I accidentally punched a hole in it taking the panel off and I know it has something to do with blocking moisture so I was afraid I might have compromised my door somehow and made it susceptible to water damage.
That’s a vapor / water barrier designed to keep water off the inside of the door panel. It is not a critical component and the duct tape should be just fine…
Alright thanks man 
You probably didn’t even need to repair it. Any penetrations in the vapor barrier for wires, window, or door handle hardware have gaps around them. I would have use the tape repair as you did, but there was no big hurry. Good job.