When a burned-out bulb is stuck in its socket, your only option is to turn it until it either unscrews or shatters. First, unplug the fixture. Then, wearing leather work gloves and safety goggles, carefully twist the bulb until it loosens. (Cover it with a rag for extra protection.) If it shatters, remove the glass shards. Then unscrew the base of the bulb by firmly pressing a raw, unpeeled potato or a bar of soap into the socket and giving it a good twist. If the spud or soap slips, press it in harder and try again until the base breaks free.
Removing a Stuck Light Bulb
What to do when a burned-out bulb is stuck in its socket
by Mike Wirth