After foreplay on my breast last night, this morning i woke up and it was really red..?

I only just realized it but after my bf rubbing my boob last night fairly hard , all the bottom part near my armpit is really red and there is a fingernail sized bruise, but it does not hurt. Please could you let me know when it will go away and how i can help it and wether i need to see the doctor? im only 15;