It's not an error, but it's different enough to keep if you want to. I put stuff like that in an "Oddities" box and pull it out now and then to show friends and family in what we call "Show and Tell". Remember, every coin has a story to tell.
When I first started looking for errors (yesterday) i read about a coin that had a staple that clearly was imprinted on it.since then i have found 1 or 2 myself.? Interesting coin.