For the OP, my DD fell off the bars last year and "tweaked" her back. She hyperextended her back and it hurt at the time; but then she said she was fine. At her next practice her back walkovers were a hot mess and her coach and I had her stop and talk to us, she said her back was hurting. I took her to a pediatric sports ortho the next day. At first he had her not doing anything that hurt at all for a week (so no bridges, cartwheels, BWOs, bars...); but it still wasn't better. She then was off of everything for almost 3 weeks - no exercising at.all. No PE, no playing on the playground at recess, no gymnastics practice. It was slow; but with the total rest it got better.
He did do x-rays first to make sure that it was just muscular.