I can help you I had that problem on my 1988 cutlass ciera and the answer is that one of the lights on the back not the third small on is not working. Open the trunk take out the bulb itself and check the wiring. That what was wrong with mine someone didn't have it wired right. Hope this helps you out.
Check the switch on the brake pedal
Stuck brake light switch.
Check the brake light switch. It's under the dash, connected to the brake pedal. If it's adjusted wrong or faulty, it could cause the brake lights to stay on. If you can use a meter and tell that the brake light switch is ok, next test the turn signal switch. Sometimes they short out and leave the brake lights on. You'll have to pull the steering wheel to do that.
If the tail lights were hot during the swap you may have broken the filiments. Bumping a bulb that is on or been on recently can cause the filiments to fail. Remove the bulbs hold them up to a light and see if the filimant is intact.
brake light switch would be most common cause
BAD BRAKE LIGHT SWITCH AT TOP OF BRAKE PEDAL
Possible ground issue at the taillights.
The BOO (Brake On/Off) Switch may need to be replaced. If it is bad, it would cause the brake lights to NOT illuminate when the brake pedal is applied.
Blown fuse or defective brake light switch.
Most likely a fuse.
The most probable cause is that the brake light switch is out of adjustment.