If you borrowed money from someone who isn’t an authorised lender, you haven’t broken the law. The person lending you the money might have broken the law, if they are lending as a business without authorisation (ie not loans between family & friends).
You can find out whether a money lender is authorised by checking the register on the FCA website at www.fca.org.uk
If you think a money lender is operating without being FCA authorised, in England or in Scotland, you can speak in confidence to the Illegal Money Lending Hotline on 0300 555 2222.
The illegal money lending team will offer you support, and will make sure that you are kept safe. You will not be forced to give evidence or testify in court, but it’s possible that with your help a loan shark can be stopped.