All kind of things can cause injection site sorness.
The amount of Ba, how fast you pushed it, if the gear was not warm enough, how deep , not deep enough, if you wiggled the needle while shooting .ect..ect…
You get the picture.
If you do a search you will most likely find thousands of post on this subject.
It has been beat to death .
Every other day the same question pops up.
Someone with more knowledge of the subject needs to write up a sticky .
Soreness is part of sticking something in through your skin and into the muscle .
It is gonna hurt sometimes.
Just make sure you keep everything nice and sterile so as to rule out infection.
I’ve been doing IM ( mostly test-e) for twenty years and it seems like every third shot or so I get some slight swelling and sometime redness.
I just don’t worry about it . I shoot it in the front thigh on non-leg days.
Take a couple Advil, put a warm pack on it , drink plenty of fluids and come back and see me in seven days.
If you went to the Doc that would be what he would say .
Oh Yes ! Pay the receptionist $150 on the way out .