You have mass, cyst
in the breast along with underarm pain crossing the chest and hurting more on the backside of right lung.
If you are before menopausal age no need to worry much.
What you need is
1) A thorough clinical examination
of both the breast
3) USG - of both the breast.
The commonest are the fibroadenosis
or cystic changes - both are pseudo lumps.
If the above is not conclusive - better to do excision biopsy
and arrive at a diagnosis by the biopsy report and further treatment as per biopsy report. Don't prolong by observation.
Regarding the pain in the chest and pain in the right back side need separate investigations like X-Ray chest