Toilet Flange Problem

I started putting down new ceramic tile over a conctete slab in an existing bathroom recently. When I removed the toilet I saw a bad problem. The hole in the concrete slab is just wide enough in diameter for the 3" PVC drain line. I cannot fit a flange over the outside of the pipe because there is no space between the pipe and the slab. Additionally, the tile raised the floor level 1/2 inch higher than the pipe. Can anyone recommend a way to re-install the toilet? Thanks.

You can place a rag inside the pipe and bust out some concrete till you have enough room or you can get a inside the pipe flange and make that work.

Thanks for your suggestion.
I ended up removing about 2 inches of PVC from the drain pipe, inserting another piece of PVC that fit inside the drain pipe, and then securing the flange to the outside of the new PVC. It looks great!