Pimple under arm. Am not understanding?

Hi doctors I had breast usg including both armpits on September 2023 as they had found a cyst in December 2022I don't have any history of family breast cancer nor I have symptoms so for safer side I repeated the scan againThey found 0.2mm birads 2 cyst in right breast which is of same size From last 1 week I found a painful pimple under my right armpit which was causing little discomfort now no discomfort but it still exists I checked if it's lump but didn't feel anything hard when pressed i felt only skin it looks like pimple it's so small but I have anxiety So I have attached a pic of it and circled the pimple or boil I don't know what it is is this breast cancer or do I have to repeat scan again am not understanding Thanks in advance