Chest... issue?

Ok I wanted some answers about this because it kind of scared me. Today I noticed my chest area was kind of sore. On the left side close to my breast/arm pit area. Is this something serious? I got scared because it's my left side. Could it be from...

sleeping wrong or a sign my period is coming soon *I haven't had one yet this month* or something like that? I haven't really noticed anything like this before. So am I ok or do I need to tell my parents? It doesn't hurt when I breathe or anything like that... it just hurt a little bit,
BTW... my age is 17.
Please help?!

If you were doing any out of the ordinary physical activity in the last day or two, it might just be muscle pain. Also, some women do get tender breasts right before their period.
If it just lasted a couple of seconds, it could have been gas too.

If the pain feels like it's inside your chest, and it's intense or persistent, then definitely tell your parents.

Well I was walking around the mall today... I was gone about 3 hours or so. That might be why. I asked just to be safe. And if it happens a lot or if the pain gets really bad, I'll let my parents know what's going on. Should I maybe write this down so if it DOES happen again it'll be documented?