Grammy-nominated rapper Post Malone was hospitalized Saturday after experiencing a “stabbing pain” in his body, he announced on social media. The Syracuse-born artist, whose real name is Austin Post, said he woke up to a “cracking sound” on his right side. “I’m having a very difficult time breathing, and there’s like a stabbing pain whenever I breathe or move,” Post wrote in the announcement shared on Twitter. “We’re in the hospital right now.” Post, 27, canceled a concert in Boston on Saturday night, and said fans’ tickets would be valid at a yet-be-rescheduled show. The rapper injured his ri…