Burned
I was sleeping and I felt something painful on my wrist ! I removed my apple and there you go ! It's a small blister ... why !!!!! It's been a long time i'm using it :(
Apple Watch Series 4, watchOS 9
Question marked as
No, it doesn't matter, it's just a rather unusual place to wear a watch. I would IMMEDIATELY stop wearing your watch.
You need to contact Apple Support for help here. Your tag line suggests you have Apple Watch 4, which is now pretty old, and my guess is the battery is failing and it got hot while on your arm and particularly the way you wear it, was likely covered while you slept, which would contribute to heat buildup.
I'll also ask a forum host to reach out to you so you know Apple will want to see the watch.