A National Insurance number is used to make sure you are paying the correct amount of income tax if you work in the UK. It’s a little bit like a SSN. As well as income tax, you also have National Insurance contributions taken out of your paycheck - these go towards things like job seeker’s allowance, pension, maternity leave, NHS etc.
U.K. citizens/permanent residents are automatically issued with a National Insurance number when they turn 16, but people on visas and who move to the UK later than that have to apply for one.
So, you won’t have one yet, but if you will be working, you will need to apply for it.
You can technically start working without one - you will be assigned a temporary one - but you won’t be taxed at the correct rate until you have one (and a lot of employers ask for your NIN on the application form).
See here for how to apply:
https://www.gov.uk/apply-national-insurance-numberSent from my iPhone using Tapatalk