i creat to dns with my ip
ns1.domain1.com
ns2.domain1.com

when i want to set this dns for domain2.com in onlinenic
online nic return this error:
(1169) DNS1 is not registered.

domain registrant can add this dns for domain2.com but i can not add with my panel.
why?

You need to register them at nameservers, on the registar level.

my registar create this nameserver but i can not set for other domain