Tender Breast and armpit causes?

After shaving I realized my razor was slightly rusty & a few days later I felt pain in my armpit slightly tender/swollen.......Today, a few days before my period my breasts & under arm is even more tender and painful.......Should I be concerned about the underarm swelling as well? Usually its only breast pain & swelling before my period. I'm 25 years old & conduct monthly breast exams as well as a recent one conducted by my doctor.