There are many reasons for chest pain. If it is inflammation caused by mastitis it is okay to take amoxicillin, if it is other diseases such as cystic hyperplasia of the breast, breast cysts, plasmacytosis. There are some tumors where oral amoxicillin is of little use. If there is chest pain, see if there is any pattern to the pain, such as pain before menstruation, alleviate after menstruation, repeated episodes, consider cystic hyperplasia of the breast suggest oral prolotherapy pill or breast fetish elimination. If the chest pain is accompanied by skin redness or pus, consider mastitis, possibly with amoxicillin or cephalosporin antibiotics, if aggravated may require incision and drainage. If the chest pain is accompanied by a lump in the chest, an examination suggesting other diseases should be treated according to the cause, not all diseases can be treated with amoxicillin.