Lucky you, I did the same dumb thing a few weeks ago.

I hope you haven't done any unreversable damage.

You have to disassemble the N9, but not far.
Look for the nokia_n9_rm-696_service_manual_12_v8.0.pdf
it tells you the steps in detail.

Follow the document to step 15, removing the display.
(For readers which haven't forcefully removed the tray, you can access the screw below it by bending the plastic carefully. This will damage nothing and its better to leave it in)
Afterwards you can access the sim adapter.

Now the problem. The sim reader has springs inside. (Shown on the left in attached image)

A normal sim pushes them down and releases them when pulled out. (shown from the side in blue in the image, left is up, the spring is shown as black), your adapter has a hole. The spring jumps into the hole when pushing the adaper in. (shown in orange in image) When you pull it out the bottom border collides with the spring and prevents pulling it out.

Luckily Nokia has included a tiny hole above each spring.

So now you have to push each pin in a row down and carefully push the adapter up meanwhile. So that the spring can slide under the bottom of the adapter. It takes a bit of dexterity and endurance to get everything to align, but you will get the adapter out.

Don't apply to much force on pulling the adapter out, if you bend the pins with excessive force, you have bigger problem!


Edit: A simpler way for you may be to cut out a thin strip of sturdy plastic and slide it along the adapter so it slides over the hole and releases the springs. With the tray still in there too, I haven't found a plastic sheet slim and sturdy enough to push it in.