Those growing concerns of Paul Pierce missing Monday’s game against Minnesota and his absence at the Celtics morning shootaround yesterday can be shelved, especially in a season with so many injuries to this team. Pierce, listed as a game-time decision before last night’s 98-93 victory over the Detroit Pistons at TD Garden, has recently struggled with an ankle injury, and has experienced minor bumps and bruises all season long. But the only thing that might have been bothering him last night was a little lack of sleep. The Celtics captain welcomed a new addition to his growing family Tuesday when Prince Paul Pierce was born. Pierce broke the news to Sean Grande and Cedric Maxwell on the WEEI postgame show, but did not mention it to reporters before his exit from the locker room. “(Tuesday) at 8:21 p.m. Prince Paul Pierce was born,” Pierce said on the postgame show, promising Grande that his son would spell out his name and not go by a symbol like the other famous Prince. “So for the next 18 years, world, Celtics fans, look out.” Pierce gave his new son a nice welcome into the world with 17 points, six of those coming in the fourth quarter when it looked as though the rest of the Celtics were just as sleepy as a father in the first 24 hours with a newborn.