See a Doctor
Any new lump in the breast should be a cause for concern, best handled by seeing your gyne or primary care doctor. While most cancers are not painful, it is not a reliable finding.
Hopefully, your doctor will be able to alleviate your concern or refer you to a breast center/surgeon for definitive evaluation. I hope its a false alarm--good luck.
...Do you have a follow-up question? Consult Dr. Rosen, a General Surgeon with 28 years in practice: