I had the exact same problem last week and was told exactly the same - expect I was told to take pain relief medication and not prescribed with any pain relaxers. The A+E doctor did test my urine to rule out any kidney problem which was fine.
If this pain has not settled, make an appointment to see your own doctor. It still may be muscle spasm, but kidney problems need to be ruled out.
Observe your urine. Urinate into a clear clean jar - if it is foul smelling, cloudy, dark - any of these could indicate a urinary infection.
Make an appointment to see your doctor.
THat is where your liver is, you could have liver qi stagnation, you can google it it is Traditional Chinese Medicine. Of course could be something else, might want to get checked out again. Good Luck!