Gap Appeared in Teeth, No Idea Why? (photo)

about 5 days ago I realized I had something "black" between my teeth, I thought it was a piece of food but as I brushed my teeth it didn't go away I put my tongue up to the roof of my mouth and it covers the gap, ive always had nice teeth and this has just come from nowhere, gums have bled a little bit when brushing,WHAT IS THIS? thanks :)

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