Nikon D5100 camera issue?

Hello! I am currently looking for a solution to a problem with my Nikon D5100… I have owned it for 2 years now, and have had no issues up to now. Last week I switched lenses (the same way I always have) but when I take pictures now, something is obstructing the view internally… I have tried several lenses to make sure one of those is not the issue, so I know it's internal… Anyone know what's up and how to fix it? Example of a photo showing the obstruction attached… I have not dropped it, so I'm not sure how or why it started doing this… Thanks!

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