That is a real problem and I have been there even on a new barrel. Thy putting the pin back in and then using both hands on the trigger guard and it may open if not there is a post on here some place that says to put in vise and hit with a rubber hammer, I dont care for that advice

some times you can remove the barrel pin and pull barrel forward and down and wiggle it a little and grip trigger guard and will come loose, there are a number of post here on how to solve problem good luck
Deaconllb