Over a week late on my period

Should I be concerned? I haven't been sexually active in over 7 months. I just got off of my birth control 2 months ago. My period came on time last month, but this month, not so much.. Should I be worried? Should I be worried about having polycystic ovaries? I do have a dermoid cyst on my left ovary, could it have something to do with that? Should I go back on birth control to get it regulated again?