I've had a similar experience with some swelling in the glute. I think it was from a shallow injection because there was some redness, very slight amount of heat, but it got better every day after the injection. It was not an infection in my case. I kept an eye on it and decided that it may have been due to some slight irritation from the BA.
Or I also thought that I may have injected close to a nerve and the glob of oil was putting some pressure on it. I'm not really sure. I was also injecting 2ml at a time, so that didn't make it easier.
I'd say skip that site this time around and go back to it if you want in the next rotation if it clears up.