Open My Computer -- right click DVD drive (probably D: or E;) and click "eject".
I'm not being patronising, but using sharp objects on a PC with electricity going round it is kinda dangerous. Unplug the PC; use a thin screwdriver (very carefully) and open the drawer. Sounds like the rubber band which controls the drawer mechanism may have came adrift.
Given that a new DVD-ROM drive cost about £12 click here
may be best to replace if there is a hardware failure,