> The best I can do is create another group and start counting from (0-9) again.

Yes. Or use smaller groups. When you count all the fingers on one hand, make a sign like this in the dirt: V

When you get two V's, scratch them out and make this sign: X.

If you get four X's, XXXX and need a fifth X, then scratch them out and make a bigger group, say L.

It's very easy, just keep making bigger and bigger groups. Groups of your groups.

(I leave it as an exercise to the readers to explain to our caveman why the Roman idea of grouping your groups into bigger groups, which seems pretty intuitive to me, is inferior to positional numbering).