I Was Doing A Simple Gymnastics Move- A Roundoff But

I was doing a simple gymnastics move- a roundoff but when I did the rebound (I was about 3-4 feet in the air) I landed on my butt/lower back. I got up soon after but it is very painful and sore to move still 5 hours later. Should I be worried? And can I play water polo tomorrow at school?
Alexandra king.
Age 14