Burn on my wrist

There are other people that have had allergic reactions to materials in the Apple Watch. You can search the forum to find some.

There are a lot of people allergic to nickel, which is a material used in the Apple Watch (or at least some models)

https://support.apple.com/en-us/HT204665

You should stop wearing the Apple Watch, and contact your doctor and any specialists your doctor recommends. Take your Apple Watch with you.

Unless you feel it was from heat, as in the watch overheated. If that is the case, then take it to the nearest Apple Store and have them check out the watch for a failing battery.

• Yes! Three days after I bought a series 5, watch got very hot while driving. It was dark, but when I got home, blistering had formed. Called Apple, again. Already had an appointment due to excessive battery drain the first two days of having the watch and sound not working properly. Apple escalated the watch to an “investigation” so when I went to an appointment the next day at the store re: battery drain, sound and now burn, store wouldn’t let me return. Just found out that Apple, whose engineers have been conducting remote testing (never mind that the watch hasn’t had battery power or been turned on), deems the watch hardware functioning properly and now, after a week and one day of owning this watch, says I’m “approved” for a refund. WTF, Apple? So back to the apple store to make the return. Hope Apple doesn’t sell my returned watch to someone else. Really poor, even dangerous, business conduct, Apple.

That's an allergic reaction. Have it dealt with by a competent medical professional instead of trying to place blame on Apple.

Apple isn't responsible for your medical problems.