Hello,
The pain at the injection site is most likely caused by
thrombophlebitis. It happens whenever an inflammation occurs along the vein as a reaction to the injection, more so when a contrast is given. You can consult a physician who may prescribe an anti-inflammatory, antibiotic and thrombolytic along with ice-pack applications.There is no need to worry as the reaction subsides within 10-14 days as the swelling clears.Take care.