Hello. May I Note I Am A Kid. But, I've

Hello. May I note I am a kid. But, I've been having sharp, quicks pains in my lower left rib. (Around the bottom center) I thinking its a strained muscle. My dad thinks that's what it is. There is no marks and I realized it was hurting when I went swimming around 1:00 today. I felt these pains before but this one lasted longer than normal. I am a active Premier soccer player. I would like help on this to find out what I can do. Thank you for your time.