+4 on Belter's diagnosis. I had the same thing happen. Wondered how the axle could increase in diameter with time. I could just get it out but it did not come easy. It was only tight on the right side (from riding position view), which is the larger diameter end. I put some calipers on the diameters and had a measurable difference. I put mine in a vice (nylon jaws) and very carefully reshaped it.
Ducati: 2013 848 Evo, 2000 ST2, 2008 Monster 695
Non-Ducati: 2009 R6 (Track Bike), 2008 KTM 250XC (Practice Bike)