My husband woke up with a very large bruise on his right hip. It is purpleish, but pretty large squareish area, one part has the same pattern as the elastic band on his pajamas. It isn't dye, they're white. But the bruise has that pattern like blood pooled there? It was very sore the first day, pain has subsided but bruise still there. He didn't hurt himself, just woke up with it. Any ideas re the cause?