If you went from R Glute to L Glute, your injection technique may not have been as clean with your off hand. I agree with Iron Game that if you didn't feel anything the first time, it is unlikely that the Primo stung more the second time unless the area was sensitive from a prior injection or you just got an area more dense in nerves. Personally, I have to give an area 10 days to 2 weeks before shooting there again to avoid extra sensitivity. Also, I like to poke the injection area with my index finger to feel for nerve density, and try to locate a "dead" spot.
Sometimes, extra movement with the needle or piercing a vein will cause extra pain. Check for swelling or bruising.