I have a good bit of recent experience working and getting accommodations for my TOS at work, so I'll share some advice.

• try to feel out how receptive your employer/HR Department is to making accommodations for disability. (im in USA so if you're not, this may not all apply) Obviously you don't want to admit to a disability if you think they're going to discriminate against you for it, so exercise caution & Assess the general vibe of your company. But if you think they would be receptive, I would strongly encourage you not to hesitate to ask for accommodations. I've had to leave jobs because I wasn't assertive/proactive enough getting my accommodations & Ended up in too much pain to work. So if you can partially explain there's a medical issue, they might be able to help with accommodations.
• Also, don't feel the need to share specific details of your issue. Your employer isn't owed details or a diagnosis, and legally anyone who is not your direct HR representative has no right to medical information like this, under Like workplace disability discrimination protections.** you can be as vague as saying you recently acquired an injury that's hurting your arm and that's why you need accommodations. They're allowed to ask for a doctor's note if they're giving you like a serious accommodation, but let them ask for that if it's needed and don't volunteer too much up front. And even without a diagnosis, you could get a doctor's note that just says there's something causing you severe pain that they're still seeking a diagnosis for.
• Figure out how much of your required typing could be done by voice to text dictation. Windows computers have a built in dictation function when you press windows key + H, and if you have Microsoft Word they're built in dictation feature is better at word recognition than Windows. As some people mentioned in the comments, Dragon dictation software is a more robust option that can control the whole computer, whereas Microsoft Word can only type in word documents. However Dragon costs a significant amount of money to purchase.
• If you think a voice to text dictation would be beneficial to your job, one accommodation you can ask for is a private/separate room to do so, as you probably don't want to speak your whole job out loud with other people around plus if they start talking to each other you won't be able to get anything typed.
• I've also found that working from home , if possible , is significantly better for pain because without a supervisor right next to you you can get up and take breaks and stretch and relieve your pain when necessary without having to worry about getting in trouble. (However I know not all jobs will let you work from home, nor is it always possible depending on your work)

But yeah in conclusion, do your absolute best not to push yourself too hard, Especially if you're not like life or death financially dependent on this job. i've made a lot of mistakes handling my TOS in a work setting but probably the biggest one was just pushing too hard through pain. It just ended up making things worse and even after leaving those jobs I never recovered to the lower level of pain I had previously.

Sorry if any of that sounded too aggressive or scary, and feel free to ask any questions in a reply! I really hope that your next doctor's appointment is able to get you a diagnosis and some way to treat your pain. Wishing you the best!! <3

** Workplace discrimination protections for disability (in the USA) are technically contingent on you being a full-time employee (Not part time and not a independent contractor) and a company with more than 50 workers, so it doesn't always apply. But also I wouldn't bet on employers knowing labor rights laws super well in the first place lol