The writing process is different for everyone, so it's important to figure out what works best for you! If you find that going back to fix misspelled words interrupts your flow, then you can absolutely keep typing without fixing your errors right away. Your process is personal and you shouldn't feel like there's a right or wrong way of getting your ideas on the page.
If you use a word processor program with spellcheck, it should be fairly easy to go back and fix any spelling errors later. I know plenty of writers who freewrite without fixing anything. When I write, I prefer editing along the way, but I can recognize why this strategy doesn't work for everyone. Happy writing!