Take it to motor rebuild shop. You could probably DIY but rotor windings must be:
1. Insulated from the laminations.
2. Wire cannot be scratched or kinked.
3. Varnished properly (usually dipped)
4. Reconnected to the commutator or slip rings.
That's in addition to being rewound with the same number of turns, in the right direction and turns nested properly so they don't move against one another. That's what the varnish is for. There may also be some kind of metal clip to keep the windings from moving outward when running. I work at Lincoln Electric and seen a lot of rotors made over 40 years.
Not saying you can't do it, but there's a lot more to it than you'd think.