Did she look at your back?
And the strength of your core. ITB band kicks in when core fails. It also tightens when you lower your activity levels and can be irritated by biking if you're new to it.
Plenty of painfull rolling, tennis ball to the glute area and stretching - all muscle groups that attach to the core, and ITB stretching....
It can be managed quickly but you have to bear some pain.... GWS