I did the same thing last night 😟 Yet it is proving a lot more difficult for me to get the darn thing out for some reason! I've tried the paper clip and hair grip suggestions, plus the sticky tape on business card. The SD card cannot be seen (it has gone past the little flap bit of the CD drive and I think that's what's stopping it from coming back out of there). I can feel it with a hair grip but I've been fishing around inside for a while and it won't budge, I really don't want to do any damage.
I rang up Apple and they said I would have to take my iMac for a service so they can assess the damage and get the thing out. This will NOT be covered by my Apple Care which I'm a little annoyed at. Does anyone have any idea of the costs I'm looking at if I take this option? (UK)
I'm tempted to have another go, as the SD card has some pretty important stuff on 😟
If anyone can help, it would be much appreciated!