Hole blown in head?

First, I had a spark plug to blow out from the #3 . Threads were stripped, so I inserted helix coil and replaced plug. I drove like it never happened for about 2 months. Then I heard the old familiar sound like a cork from a bottle. I pull over pop the hood and to my surprise the plug is still in. However, there is now a hole almost the size of my pinky finger beside the plug hole. I mean I can the outer part of the helix coil threads. It continues up the wall of the head. Now my question is, is there probable internal piston or block damage? Or would it be worth replacing the head gasket and any other parts needed for that project? Also, I know that my temperature gauge never read above 195. Please offer some advice.