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I've had good results with these, and they're fairly cheap.
Ice packs, like someone else said. If you can, take a weekend off and avoid using that hand as much as possible. You'll feel totally useless, and basically all you'll be able to do to occupy your mind is watch TV, but it'll help.
You can also try looking up "artist wrist stretches" online. Overuse issues are really common for artists, so there's a lot on the internet about it.
And of course, talk to a doctor if you can. They can give you advice more tailored to your specific situation. Your bosses, as well. If they have posters about it up everywhere, I'd imagine they'd probably have some ways to help.
Not sure if your hand issue is the same (I have arthritis in my hands), but I find that doing a little EPP actually helps - it's like a brief bout of exercises for my painful joints. It takes me forever to complete projects, and I have learned to just be okay with that. I'm horribly slow at machine-sewn projects as well!
That being said, I have on occasion gone overboard and worked for an hour or two instead of 15-20 minutes, and always pay for it. Short bursts, once or twice a day, are my sweet spot. I also wear these fingerless compression arthritis gloves when I work: https://smile.amazon.com/Doctor-Developed-Compression-Gloves-Handbook/dp/B06XWWN4D3?ref_=ast_sto_dp&th=1
An alternative is gloves like these. I bought the ones I linked and they really help, I think sometimes stores like Target and Walmart have similar ones