Cats are pack animals, and in the wild, once a kitten is weaned, it moves away and forms its own pack.
As a domestic cat, your queen has her own patch your home and garden, but her klitten has not moved in, he has simply become an adult cat, and therefore, competition for the position held by his mother - hence the spats.
Remember, each will have forgotten that they are mother and son, they are simply adults who find themselves sharing territory, and that will mean the incumbant defending it, and the interloper trying to take over.
You will find that your growing kitten will adapt to the new situation quite quickly, and things will settle down. Remember, all cat playing is training for the adult business of hunting, and fighting for territory - don;t be too sure he wants to 'play' with his mum these days, but they will both adjust, just leave them to sort it out their own way.