YOU SAID:
my arm hurts because i got vaccine today
INTO JAPANESE
今日ワクチンを受けていたので腕が痛い
BACK INTO ENGLISH
My arm hurts because I was receiving the vaccine today.
INTO JAPANESE
今日ワクチンを受けていたので腕が痛い。
BACK INTO ENGLISH
My arm hurts because I was receiving the vaccine today.
That didn't even make that much sense in English.