Tinnitus describes a noise heard in the ears or generally in the head but not as a result of externally generated sound. It is common and generally harmless. Investigation may be necessary with a hearing test (audiogram) or even an MRI scan of the hearing and balance nerve region of the brain. Severe cases of tinnitus may require referral to the tinnitus retraining therapy service.
It is often useful to get information from the British Tinnitus Association https://www.tinnitus.org.uk/.