Typos matter because they need correcting. It’s important to work towards your thesis being as clear and polished as possible – but it also helps you to know that perfection is an ideal. Most PhD candidates have to complete corrections of some kind after the viva.
After submission you don’t need to scour your thesis to identify mistakes. If you find one, make a note in some way. Be prepared to explain something that’s unclear or incorrect. In general, identifying mistakes is less important than spending time to identify your strengths.
“What potential corrections have I found?” is a much less useful question to ponder than “What’s good about my thesis and research?”