Sorry if it's wrong sub for that kind of question but I can't think of any other.
It's dangerous to walk around with uncut toenails, especially in a times where people walked more and didn't have smooth roads. I can imagine you can just use your teeth on fingernails. You can cut your hair with any blade (especially if someone helps you). But what would you do with toenails if you live in a primitive society with no access to a complex tool like scissors or clippers?
Oh, this is certainly a good sub!
Mentioning previous answers here is intended as a starting point, not to discourage discussion. More questions, data, or debate is welcome.
"What did people use before the invention of the toothbrush, floss and scissors?" at https://www.reddit.com/r/AskHistorians/comments/12m6x7/what_did_people_use_before_the_invention_of_the/ , with answers by /u/Aerandir and /u/speculativereply .
If you have more questions on hygene, that's from the FAQ, https://www.reddit.com/r/AskHistorians/wiki/faq , the section on Science And Health / Hygiene And Healthy Lifestyles.