Just need to clarify - is piglet still with it's mother or is the age of this piglet a typo?
If you worm the sow now, some of it will pass through the milk to the piglet.
As landroverroy says if you are bottle rearing. It would be a good idea to start looking for a companion for him too if this is the only piglet you have.
I usually worm my sows/gilts a week or 2 before they farrow which usually prevents the litter being born with a worm burden & if bringing her inside to farrow, a good wash of her underline helps to prevent the piglets picking-up worms that way too.
I worm my litters at 8/9 weeks old, depending whether I am Ery vaccinating potential breeding or meat weaners.