Apple Watch sensor burn

I’ve had my Apple Watch for about 2 1/2 years and love it but today I started feeling itching and burning under the sensor area. I promptly removed my watch and noticed a red, itchy blister bump. What’s going on? I’m now reading all these posts regarding other users experiencing the same thing! My watch just updated recently. Now I’m wondering if this could be related? Apple, do you have any answers?!