If you have the yellow light of death then:
1. First shut down the system by flipping the power switch on the back off.
2. Hold down the eject disc button.
3. While still holding down the eject button, turn the power switch back on.
4. When the green light comes on, wait a few seconds then tap the eject button a couple times. The disc should come out at that point.
This may not work on some of the older models.
If not then have you tried to hold down the eject button for 10 secs might work for you. other than that you could remove the faceplate and take out the Blu-Ray drive to get it out but this voids your warranty. Also you could send it back to Sony if it is still under warranty.