You can get a sheet metal screw which could be inserted into the hole. After this, you could pull the collet out easily and your 3D printer is ready to print the desired 3D objects. Buy Best 3D Printer 3D Printers for Sale at Best Prices 3D Printers Online...

There is a collet stuck in there. It was probably in there without any tool in place, then the collet nut was tightened. With no tool filling the hole in the collet, it collapsed and became small enough to be pushed too far in. Fortunately these collets are soft steel. Find a sheet metal screw that you can screw into the hole. That will allow you to pull the collet out. Discard that collet. These collets come in at least two sized to accommodate different sizes of tool shafts. Unfortunately the spare one you have is one of those sizes, and the one you extracted is probably the other. But they don't cost much and you can buy them where you buy dremel tools. Good luck, Al K