The British pop star was photographed with two of his fingers taped together in London late last month.
There was also a bandage wrapped around his right hand and wrist, and scratches were clearly visible on his knuckles, and now the 20-year-old reveals it's all because he was fooling around in the studio.
He says: "We were in the studio and decided to do a bit of skating, but the floor in here isn't the best. I fell off and the board went over my hand. It hurt so much. I was trying to do a trick and went flying. It was a bit stupid."
And his bandmate Louis Tomlinson adds: "It makes me cringe thinking about it."