Fever is the big thing, but a fever can also come from a bad shot/ reaction at start of cycle too.
Watch it and see if it gets bigger. If you start feeing sick and/or runing a temp I'd get to the Dr.
Some shots make for a red spot like a hard slap. Ive had them hang around for like 10 days.
Prolly hit a nerve.... Limped like I'd been shot, but no fever and felt fine.
THis happens even with the best HG steroid time to time.
wash with hot soap and water before shots goes a LONG WAY to prevent infections.