I might have used a wrong word (I'm not an english speaker). Not sure if it actually is muscle soreness (I believe it is also called muscle fever). I was a bit tired from the last training, and I tried to do a back round kick and I felt a pain in the left glutes.
I don't know, I guess overextended the muscle, now I feel a bit of pain when doing certain moves. I don't think is muscle fever, I experienced that when I started karate.