Why is my turn signal socket like this?

Ever since I bought the car a couple months ago, my driver's side orange corner light has been noticeably dimmer than the passenger side.



This morning I woke up and noticed my left blinker was blinking twice as fast, along with a warning for a burnt out bulb. After work, the warning went away and the blinker blinked just fine.



When I got home, I pulled the socket for the turn signal out of the headlight and found this:





The light is dim, but it works. I tried swapping bulbs, but the light is still dim. I swapped sockets and the problem followed the socket.



Why would it be like this? Is it a danger to continue to use this? :help: