What if a coil contacts a part made of nickel alloy during process?

Ideally, you don’t want the part to make contact with the induction coil. There are ways to avoid doing that...

...encapsulation with a ceramic coating is one option. However, if it accidentally touches the coil, it could become part of the circuit of the coil and there could be arcing. You could also lose heat to the water-cooled copper. It’s best to reengineer the process so the part doesn’t touch the coil. You can put a ceramic insulator inside the coil, or coat the turns of the coil with a ceramic coating. That way it doesn’t come in contact with the bare copper.