These are sebaceous gland
cysts.They are formed when the duct of gland gets blocked and gland keeps secreting. Yellow substance is sebum, its secretion
of the gland along with dead cells and may be pus in addition.
Few things which can help are taking steam, cleaning face few times a day, avoid face getting oily or sticky for long,take course of antibiotics for few days and good parlour or skin specialist can clean up your back or white heads on nose.
Hope this answers your question.Regards.