Ignition Cylinder

[chc]

Recently I experienced difficulty of inserting the key to the ignition cylinder. Since the key is a duplicate, I thought the original key will have no problem. But even with the original key, it is still difficult to get the key in, is this mean the ignition cylinder is getting bad or is there anything I can do to improve/fis the problem? It is 89 300E with 120,000 miles. Thanks