Don't worry too much, since it has happened, if you don't feel any discomfort, don't assume anything bad.
However, better not to continue the treatment. Not only the growth plate, but the region is also close to the reproductive organ which is sensitive to temperature too.
Perhaps can consider magnetic therapy "MagnetoPulse", also a deep treatment so-called healing promotion but no thermal effect. I usually use this for clients with hip problems, although the effect is not very significant, it is safe to the hip region.
All the best.