Push out the side retaining pin. Push down on the stuck pin, with pointy tip of the L shaped tool from the cleaing kit push it up from the inside's of the side pin hole.
At least that's what I did when I f**ked up and put lock-tite on my muzzle break thread and everything spilled around and in the pin hole. I have to jerk it for a while working up and down until the lock-tite came off and I and worked the pin loose. And I sprayed it up with some gun solvent and oil in hope of cleaning the crap from the lock-tite.
This might not be the best idea but its what I did. If you wish, wait for a second opinion.