You don't mention if this is a first encounter with a new boyfriend. Several different scenarios could be happening. If you used a condom this could be a latex allergy, which can be extremely dangerous if you're again exposed to latex. You could also be having an allergic reaction to any lubrication, or bc gel or foam you may have used (or any "enhancement " jelly or lube). If it's just due to excessive friction then ice and rest may alleviate it. Also if you're using any antibiotics you may be developing a yeast infection (common with strong or long term antibiotics).
I would certainly visit with your gynecologist if your symptoms haven't improved within a day or two!
That is usually caused by a popped/(Blown) blood vessel. Same thing happened to my ex and I. It is important to make sure they evaluate it properly, just keep an eye on it, ice it.
That happened to me as well but it took about an hour to go back to normal. What I do in almost all kind of cases where medicine does not help is remove the one factor that causes any kind of inflammation in the body. Acidic environment. Foods that cause acidic environment is meat, milk and products, sugar, gluten. Eat food like peas, sweet potato, a hell lot of green leafs, brown rice, kinoa, buckwheat, red/black fruit etc.