Hi
Take a thin bladed screw driver, open the bolt most of the way. You can see the bolt release on the left side, push it down with the screw driver, the blade needs to be skinnie enough to fit in to it. Push down near the reciever, pull the bolt out the rest of the way. You will need to remove the screw driver once the lugs clear the start of the bolt release. If that does not do it, remove the rifle from the stock and push the bolt release with your finger. This might be the best idea and check to see if the little square in front of the trigger is binding some where. Try it out of the stock, if it works, it maybe rubbing on the stock some where.
Good luck
jim