How Did Cavemen Cut Nails?

They could theoretically have used a flint edge to trim them, or a rough stone to file them down. However, we don't have any firm evidence of 'cavemanicure' at all, since no fingernails or toenails survive from any Stone Age burial sites.

How did early humans trim their nails?

There have been various literary references to people cutting their nails throughout history, but the tool of choice is almost always a small penknife or a blade. Depending on social status, cultural tradition, and place in history, carrying a knife may have been as common as putting on clothes.

Did cavemen have to cut their nails?

It's unlikely Palaeolithic (and before) man manicured nails. If you're talking about the maintenance of finger nails then they may have broken off, bitten or chipped away at them if they got too long for whatever reason.