Stupid tool question

[Captain Knievel]

So I got air tools for the first time, and I attach a socket to the 1/2" impact wrench. Now the socket won't come off. There was a little c-ring thing on the tip, right after the square part that the socket fit onto. It was tough to get the socket over the c-ring. Now it won't go past it to come off. Was the c-ring supposed to be an o-ring and not loose? What else could cause this? I have no other to compare it to right now.