I agree with thrig that you would need to create something to handle this case. toki pona doesn't normally differentiate between specific sides, and this is one of those cases - there are no ways to describe "left" and "right" natively.
However, I'm not sure thrig's examples necessarily do the job the way it needs to be done - poka wawa could work, but it implies something about strength, when that's not often what people mean by dominant and non-dominant side. And meli/mije are not used to describe strength in this way.
Instead, I would suggest using:
- poka lawa: your leading side.
- poka kama: your following side.
No matter what, though, if you use this you're going to have to indicate that you're setting it up as such in advance. You can still do this in toki pona itself: mi toki e ni: poka wan li poka lawa. poka tu li poka kama. This sets up that you're saying one side is your poka lawa and the other side is your poka kama.