Steering wheel is rubbing

Just in the last week my steering wheel has started rubbing on one side. You can actually see circular rub marks on the column just beneath the wheel on the left. About 2 months ago I had some tires put on and when I drove it I noticed that my steering wheel wasn't straight so I turned around, went back to the shop & told the mechanic. He told me that it was always like that ( he is the only one who ever works on my car ), but I don't think it was. So about 2 weeks ago the same mechanic fixed a leak in my tire but he also switched the leaky tire to the front with one of the rear tires. He says he didn't but I can see the mark and plug. And the steering seems rough and my hands vibrate on the wheel. I'm worried. Should I be? Thanks!