Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concerns..
As per your complain it seems that hard pea sized lump behind the ear along with ringing sensation, vertigo and neck pain
seems to be most probably due to Mastoiditis
that is caused due to infection in the mastoid bone..
I would suggest you to consult an Otolaryngologist or a General Surgeon
and get evaluated and he can do a thorough clinical evaluation and investigations like x-ray, CT Scan, blood test
etc to confirm the cause..
You can be advised a course of antibiotics, anti-inflammatory painkiller like Ibuprofen..
In case if there is associated ear infection
then along with oral medications antibiotic ear drops can also be advised..
Hope this information helps..
Thanks and regards.
Dr.Honey Nandwani Arora.