Am I wrong ?

So, today I got a tetanus shot . The doc, gave it to me on lower back more like butt . I asked if i could get it on my arm the doc refused . So I took it . My mom was present there (I am not in my teens i am an adult) , coz i am scared of needles plus my parents are protective . I told this to my boyfriend and he got angry at me asking " how could i do this to him?"
I asked him.why he is angry and he replied if he gets a shot on butt from female doc how would I feel? , Like man , I don't have any problems!!!!!! .
He is literally treating me like I have cheated on him with guy ir something !!!!!.

1 . Am I wrong? Did I do something unspeakable?
I cannot understand , pls help me guys . ╥﹏╥