Help? Hickey? Mam

I’m 17 and my Mam seen a small hickey on the side of my boob (it was barely noticeable)I told her I didn’t know where it came from and I had something like that on the other side before. She’s convinced it’s a hickey and I don’t know how to change her mind. She knows I have a boyfriend but doesn’t know I go to his house as she doesn’t let me. I’ve covered it up and I’m going to do some fake ones on my chest area and suggest it’s a rash from my new perfume. Is this a believable idea or not?