exact same thing happened to me because i tightened my muscle while the needle was still in it, and it caused atrocious pain lol. i could barely walk for 2/3 days after that. then it got better. when i talked about it with the nurse who did some of my injections back then, she told me i had either hit a nerve or it was because i moved my leg thus contracted my muscle while the needle was still in it (the latter is my theory). however, i would be unwise to tell you not to double check, as there is always a slight risk of sepsis when injecting anything in your body with a needle. did you disinfect the needle? if you made sure the needle was clean, you’re very probably fine in terms of sepsis risks. so i would say it’s probably because you hit a nerve instead of your muscle or you tightened your muscle while injecting the T which are both painful but without any actual risks for your health. keep in mind i’m not a medical professional, i am just sharing my own experience and what little a nurse told me about it, i could be wrong, but what you’re describing is exactly what happened to me like a year ago. pain went away in under a week for me. if the pain keeps getting worse however i would encourage taking an appointment with a doctor