Since this is a QT, and your not treating the fish for anything, it's best to remove the fish and place it in a a small container. Then clean out and replace all the water in the tank. Drip the fish back in and it should be fine. A lot times it can be a losing battle to get the ammonia in check in a QT once it reaches a certain point and it's better to just clean the tank out and start over with clean fresh water.
Also unless the tank was running before you shouldn't of had a big built up in ammonia unless you where feeding the fish to much.