I Am 17 Years Old And I Have One Sex

I am 17 years old and i have one sex partner , In which my mom does not know about, we both have had blood tests recently, indicating we're STD, HIV/AID free, But i have a bump below my vaginal Hole, its my regular skin color and is not itchy or burning but it feels like i little bruise and is swollen. It sort of looks like a mosquito bite. It has no hole in it or head to pop it, its just there and a little irritating. What Could It Be? What Should I Do? Im scared to tell my mom.