It is from where they call the iliac crest but at the back - you will feel tender around that area for a while as the bone tries to heal itself, and if your platelets are low, healing takes longer. It should I believe feel bruised, so not excrutiating pain, but a wee bit painful. I had 3 on the right and for my last one insisted they went into my left "hip" instead as the the right hand side still feels tender 3 years on! just sensitive souls really
If pain is unbearable then you must go to your doctor and just get them to check xxx