looks like you fried your board. I would suggest you buy a cheap toaster oven. I use Black and Decker Counter top toaster oven TR0490W. It's only 1200W but plenty strong. And use the toaster oven for reflow only. Do not cook in it. No food what so ever in it. The reflow paste has flux, and other volatile organic compounds which are very bad for your health.
I hope you are not planning on using the skillet for food.
The problem I see is that the heat capacity of the skillet is so much higher than air so when you placed a room temperature board into the skillet, the surface of the board heated very quick while the board itself took some time. You may overheated the solder mask and damaged it. Not to panic, I would still use the board. Reliability may not be as good because of moisture incursion.
Reflow oven uses radiant heat so it heats the surface (solder mask, trace) and the substrate (FR4 fiberglass board) together and evenly.
If you have any other question, let me know. BTW google reflow and I think it has some discussion/explanation on the process.
Lastly, when you cook the board, do it in well ventilated area.