Its part of the new live activities now available on the latest watch software. Whilst this icon was showing on your watch did you have a live activity on your phone for Apple Sports?
If that icon is showing and you use the digital crown to scroll up while you are viewing the normal watch face you will see the same live activity thats on your phone is now available on your watch before you get to the various widgets that are set up on your watch.
I use FotMob for football scores in the UK and i get the FotMob icon on my watch when live activities for teams i follow are showing so you can view on both your phone and your watch.
Introduced in iOS 16, Live Activities changed the way users interact with their iPhone. Instead of getting multiple notifications when tracking a...
www.macrumors.com
If there is a goal my watch will vibrate and if i lift my wrist it automatically goes to the live activity rather than the watch face but i think this is part of the setup so can be changed.
Bit more info about settings etc on this link :-
You can stop activities from hijacking your Apple Watch's display.
www.pocket-lint.com