hi welcome to healthcare magic..
a lump in a breast may most commonly be due to benign tumour of breast called fibroadenoma
.. or it may be due to malignant tumour of breast or if u r also having fever
along with lump and pain it may be infection or inflammatoion.. definitive diagnosis can only be made by examination.. so i advice you to get consulted to a near by general surgeon
.. plz just take it seriuosly and consult a surgeon.. wish you a speedy recovery..