Hi, this is a serious question about a possible injury, so get your minds out of the gutter! LOL 
Anyway, for a few days I’ve had a really intense pain in/slightly above my right buttcheek. Sometimes I can run without problems, sometimes it hurts. It definitely hurts more going downhill than uphill. When biking it hurts when i really try to put pressure on the pedal on the top of the pedal stroke. I can hardly walk after I’m done with exercise, putting weight on the leg is painful.
The gluteus maximus felt tight when stretching it. In the last few days I’ve made a point in really thoroughly stretching it, but that seems to give only very temporary relief. Any ideas what this could be? It basically appeared out of nowhere. Thanks for the help, Jan
Take a golf ball and put it between that sore spot and a wall/something hard. Move the golf ball around until you find a tight little muscle and work on it with the ball for a while (self-massage). Then stretch.
If that seems to help, then I would suspect it’s yer piriformis. I had that, can be nasty, took me 3 months of physio + no running to cure it. So try the golf ball trick, then go see a physio.
Although it was not exactly the same, I had a similar experience. I figured out it was my Piriformis muscle. When it gets tight/inflammed it irritates the sciatic nere and can cause all sorts of problems. This may or may not be your problem. I used a tennis ball and would sit/roll around on it for self massage. After about a week of torturous pain, 2 days of the tennis ball made it disappear completely. Also try googling “piriformis syndrome.” This may give you a little more insight.
Jacob
Piriformis. I’ve struggled with this a lot over the years. It becomes inflammed due to overuse, and in recent seasons I’ve become quite careful with it and really paid attention to the warning signs (e.g., tightness in that spot when running downhill or in late miles of my long runs). The golf ball treatment is good - I usually use a baseball, though. My massage therapist always focuses on that area and takes me through a series of stretches to relax it. Knock on wood, I haven’t had any serious inflammation there in about two years. It can be frustrating, though, and if it “goes” I think all you can do is the stretch/massage treatment and rest it. MIght take a few weeks to finally heal.
Yup - sounds like Piriformis “sydrome”. Good Google topic to look up