Reaction only at new site

I recently injected on my thigh for the first time, after 4 months of just rotating abdomen sites. It was within the recommended area and didn’t feel any different than it always does. Later that night I noticed a painful welt that was raised and red, and it was 3-4” wide. I returned to abdominal sites since but several weeks later and this welt has gone down but a faded red mark remains. Not sure it will fade fully given how it looks now! And I’m not sure I’ll bother trying my other thigh or upper arm, ever again. Has anyone had a similar issue? I just find it so strange. Edited to add: It was not the first shot of an increased dose, either. I am currently at 12.5 mg and holding for a while.