I have a question about my 81 mercedes 300 sd diesel.?

Today when I was about to start my car I was having trouble with my ignition. I would put my key in the ignition, but it I was struggling to turn the key. It was just stuck. I didn't know what to do except to jiggle the key while it was inserted. It took about 5 minutes before the key would finally turn. I noticed it was a little loose upon putting the key in it. Is this something to worry about or was it just one of those things and probably won't happen too often? Thanks.