Hair: After taking diksha (initiation) a Jain ascetic does not cut hair regularly. In Digambar traditions, hair is often plucked by hand (kesh-loch) as a sign of renunciation, usually done at initiation and then again once a year or during Paryushan. In Shwetambar traditions, hair is usually shaved with a razor at initiation, but some continue the plucking practice as well. The important point is that cutting hair is replaced by a ritual of restraint and detachment, not by ordinary grooming. You can read more here and here
Nails: There isn’t a separate universal rule about cutting nails described in the common ascetic practices on these Jain Knowledge pages. The emphasis is primarily on hair (lochan/kesh-loch) as a concrete symbol of renunciation. For specifics about nails in your tradition, consult your local sangh or a senior monk/ nun. You can read more about hair practices here