I was seen in er, ruq pain in abdomen tender to touch, ultrasound no gallstones, blood work normal. What could be the cause of the pain? Pn level 8.

It may somatic pain . Ruq, subcostal muscle pain could be another reason too. Hida scan may help to rule out gall bladder disease and i doubt.
It may still be. Related to gallbladder, however severe gastritis and pancreatitis are possibilities. To eliminate the gallbladder entirely a nuclear hida scan is necessary. Take 2 otc pepcid, or zantac (ranitidine) daily for a 7-10 day trial. Contact your doctor if no improvement.