You are being way too hard on yourself, go in, act like nothing really happened which is mostly true, if your boss does demand an explanation of what happened all you need to say is "sorry, I had a panic attack." If any coworker asks about it any of the following answers are acceptable "sorry, I had a panic attack" if you want to embellish whether true or not you can add "I was going through some unrelated stuff at the time and it threw me off," and if necessary "I don't really feel comfortable talking about it" it's fine to embellish a little bit because it is, and I really do mean this, none of their business anyways and if they're worth your time they will respect your boundaries anyways. If anyone gives you an opportunity to laugh it off, take it, add in any of the prior responses if you want.

EDIT: Oh, and next time someone asks you how to spell something repeat calmly after me "oh, sorry don't ask me, I get spelling anxiety" It's totally fine. If it's just general social test anxiety then you can expand the line to "oh, sorry, don't ask me, I get bad anxiety under social pressure" Modify further as needed. Again, you're totally fine.