Hi thanks for your question.
This lump is there for last 4 years.The first possibility which come to my mind is sebious cyst
.The second possibility is of lipoma
and third one could be a boil.The hole you have created is not healing may be due to infection.I would suggest you to take broad spectrum antibiotic like levofloxacin
for a week .If wound doesn't heal after one week of treatment,consult an orthopediac surgeon may take biopsy
from non healing wound to determine what exactly it is.
Hope this answers your question.