What Causes Nipple Tip Pain With An Underneath Lump?

hi, i am a 25 year old female and for a week now i have had a stinging pain coming from my left breast nipple & its tip, also there seems to be a lump underneath the nipple! it hurts if i touch it. there is no color change in my nipple or around it or on the breast. nothing itches and there is no rash! and i am not pregnant. it seems like the nipple is going inwards and i cant open it up! it hurts and scars me, nothing i have looked up it close to what i am going through!