Weird lump in ?

I am a 16 year old girl. A couple of days ago I noticed this weird bump type thing in my right . I don't know how to explain it, it is this lumpy thing on the upper part. It isn't in the other one and I am pretty sure it was never there before. My are sore but I am sure it is cause I am about to start my period. It is just really weird and kinda scary. What could it be? please serious answers only.