If it does not get better very soon, I would tell your parents to take you to an urgent care clinic, or the hospital. Yes, it can be very serious. It may be nothing too, like simple indigestion, muscle spasm, gas, mild ulcer, and lots of other stuff, but only a doctor will know for sure.
Your parents will be very angry at you for not telling them and it turns out to be more serious and costly to treat later. If it is nothing, I promise you they won't get upset.