What Causes Soreness On The Buttocks?

hello doctors, I m a male and of about 5 days ago started to experience a soreness on the inside of my upper inside left butt cheek. If I place my hand palm side down inside my left inside cheek and press against the pelvic bone there is small area about the size of a quarter that feels sore. It s close to the genital area, however there is no issues with any functions of my genital or anal area nor any soreness and no bumps or unusual characteristics of the area. I did some internet research on the male pelvic area, and I m guessing its around the publis. I m an active gym goer and worked out last week without notice of any injury to anything. This just came on slightly. I m very mobile without pain, but do notice when I stand and place my fingers inside that area and push hard and feel the soreness. I have no leg pain either. However, my uper and lower back were extremely sore after a workout this past sunday. I saw my very knowledgeable and trusted massagne therapist last night and he a very thorough massage just on my back and feel much better today, a bit sore but getting better. He mentioned that he does advance massage on the male pelvic floor so considering that. I m just perplexed that it s just a small isolated area that sore only when I push fard against the public bone and not other issues in that area? Thank you Guy in SF