"Unacceptable to wait that long for pain relief"

Teenage son attended a&e due to a head injury. He required a CT scan. Prior to this a line was put in and pain relief requested. Was told pain relief could be received after scan. He returned from scan and pain relief requested again from the nurse (unsure of their name but they were repeatedly heard telling anyone who would listen that they were the only one on shift). I asked this nurse  a further two times and the doctor who organised the scan had said for us to say but none was received. 

I approached another member of staff who was able to remove the line for my son as this had also been requested three times.

Eventually the nurse approached us in the waiting area with pain relief. I informed them that I had already given my son some that I had with me.

They replied loudly and quite aggressively that I should have told them. I explained that it was 1.5 hours since I had requested pain relief for my son. They again were abrupt and loud, this felt humiliating in front of a full waiting room.

I feel it was unacceptable to wait that long for pain relief, unacceptable that we asked this person three times and unacceptable how they spoke to us with an audience.