Suggest Treatment For A Lump Inside The Vaginal Area

I have irregular periods. Last month, it started on Jan. 22nd and ended on the 24th. On the 24th, I had sex and we were using a condom. I have a preganancy scare because the condom slipped a little, but not completely off. On the 27th, I took Plan B just in case. Now I haven't had my period yet, and I felt a lump in my vagina yesterday. What is wrong? Am I pregnant? Or is this normal after taking Plan B?