Ignition key will not turn in the barrel

May well be you need a new ignition barrel . Have you tried turning steering wheel slightly side to side to take strain off steering lock as you turn key?

I have had the same problem with my tumbler. I put the key in and try to turn the key to start the car and nothing! The mechanism is locked in place. What has worked for me is that I spray a bit of wd-40 or sewing machine oil and it seems to do the trick for a while. I would invest in a new tumbler though because this is a sign that 1, your key is wearing out and two, your tumbler is wearing out as well and needs to be replaced. I would do it sooner than later before you end up stuck somewhere. Just a thought.