Thanks for writing in.
The lump under your right buttock can be anything from a lipoma
to a sebaceous cyst
. The exact nature of the lump can only be made out after an examination has been done. The treatment can only be decided once we know the nature of the lump. This lump, however, is not related to the pain in your head.
I would suggest that you see your general physician who can examine this and put you on the right treatment.