there is no solution, you are screwed. If you want to do it right suck it up, go to a fabric store, and buy yourself a new piece of headliner material (1/8") to replace the one you butchered. Consider it a learning error that will only cost you $70 to rectify (price of teh material).

you could apply massive extra glue to the headliner around that edge and hold it on until it sticks to the roof/headliner backing board, but its going to be nasty, and the various movements of teh headliner (from wind, opening and closing the sunroof, etc.) will rip it free over time.

-rt