Your symptoms are suggestive of trauma with bruises, also need to rule out if there's any infection to the nipple. I would advise you to ask your boy friend to not be so rough with you. You can use an ice pack wrapped in a cloth over the area for 10-15 mins 4-5 times a day which will reduce the swelling and also use a hot water bag over the area for 10-15 mins 3-4 times a day so that the muscles are relaxed. You can also have a pain killer and apply a topical painkiller over the area to reduce the pain. Your nipples will be very sensitive now so wear a loose bra and wear loose breathable fabrics. If the problem persists or worsens visit the ER at the earliest.

Your BF act of foreplay seems to be too harsh and bodily damaging. To reduce pain local anaesthetic gels  ( like xylocaine 2%) and antibiotic ointments can be applied locally in addition to oral pain killers and vitamin C tablets. Go to Sexologist for quick examination and treatment.

Hi actually if possible meet Dr, till then u can apply cream n ice over it to reduce inflammation n swelling. Take mild pain killers if required.