If the flex needle was used, and we assume they inserted the needle to the depth marker and placed the flex… then we can assume the flex has a deep enough pocket and is resting comfortably in it.
The bump may be a skin flap that was not properly pulled back out on needle removal. This has to do with the bevel up vs bevel down installation discussion where if the bevel is up when the needle is inserted, a small skin flap will be made from the needle’s insertion. That skin flap gets folded under inside the wound and if the removal of the needle does not pull the flap back out, it will get stuck under / inside the wound. This could be the source of the infection as well since most skin prep is not deeply penetrating. As the skin inside the wound breaks down, latent bacteria in deeper layers can escape into the wound and flourish.