Looks a lot like the scrapes I got near 2 years back albeit totally my fault. Unmarked speed bump while I was cruising at 15mph caught me off guard. Bonked right up off the board and slid across the bumpy road surface. Had scrapes like that on my knee, hip, palm and all up the forearm. Hope you heal up soon, those sprains take a fair bit to recover from especially when it's a joint.