,I got my residence permit on 2013 .my child will born on

Hi
Thank you for your question and patience, I’m Tom and I’ll try to help you.
If you have PR then you are regarded as being “settled” for the purpose of the British Nationality Act, which is the legislation which determines whether or not a person is a UK citizen.
Please refer to section 1(3) of the act here:-
http://www.legislation.gov.uk/ukpga/1981/61
You will see in this section that a child who is born in the UK who is not automatically a UK citizen at birth is entitled to be registered as a UK citizen if either of their parents become “settled” in the UK. So, if you obtained PR after their birth then you would be able to register them as UK citizen. If you obtained PR before their birth then under s1(1) you would be able to apply for their passports straight away rather than registering first.
If you got PR after your children were born then you would have to register them by applying with form MN1. You can do this provided that the children are under 18 at the time of their birth:-
https://www.gov.uk/government/publications/application-to-register-child-under-18-as-british-citizen-form-mn1
Good luck.
My goal is to provide you with a good service. If you feel you have received anything less, please reply back as I am happy to address follow-up issues specifically relating to your question.
Kind regards,
Tom