I have dated several nurses and discussed my pet fetish (buttock injections) with them. They all excited me by admitting that they enjoyed giving shots in the bottom to men but only two of them actually gave me injections back there.
One knew that she would be on duty when I went for minor surgery requiring a general anaesthetic and thrilled me by freely admitting that she looked forward to giving me a "jab in the bum" (pre-med injection). On the appointed day, she entered my cubicle ominously hiding the injection behind her back and with cold professionalism uttered the words, "Bend over, this won't hurt". When she pulled down my pants, I requested, "not too high, please," and she obliged me with an erotically painful shot right where I sit. That evening she visited me at home, clearly pleased to see that I could only sit on one cheek, and confessed that, notwithstanding her demeanour at the time, injecting my bare bottom had turned her on as much as it had me.
The experience with my other nurse girlfriend was even more exciting. I told her that I needed travel inoculations but that I was frightened of injections (untrue but said for effect). As hoped, she opined that she had better give them to me where I can't see. I agreed and, trying to hide my eagerness, told her that she might have to be strict with me at the time. Her reply, "That's no problem at all," left me in a state of excitedly nervous anticipation for the days before our appointment. When she arrived, she promptly told me to pull down my pants and bend over for my booster shots. Testing her promised resolve, I said that I thought booster shots were given in the arm to which, as hoped, she firmly replied, "They can be, but you're getting them in your bottom." I hesitantly unfastened my trousers, letting them drop and, as I had hoped, she pulled my pants all the way down as well, repeating the instruction to bend over. Only after I complied did she begin to prepare the injections, so I spent a long time bent over in bare-bottomed antipation. It really made me scared as I spent the wait thinking only of what would happen before I could stand and get dressed and that there was nothing I could do to avoid it in my helpless, vulnerable position. Eventually, I felt both buttocks thoroughly swabbed and then three quick stings in each cheek. After it was all over, I invited her to dinner but she opined that I might not be able to sit down - and she was right!