Thanks for the query.
Better to consult gynecologist or general surgeon
once and get examined to find out the actual nature of the lump.
You may need mammography
and FNAC (fine needle aspiration cytology) to detect the possible nature of the lump.
Depending on the result you can go for treatment.
According to your description there is possibility of benign lump, so don't worry.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429