That was quite a fingering episode to result in this! Perhaps you got a minor infection (dirty fingers nicking you?). Not sure. But if you have 'terrible pain', then you should see a doctor. At your age, you should be able to go into the doctor's exam room by yourself and talk to a doctor openly. I have sons at 16 and 14 who get to decide if they want me in the room or not when they see the doctor. So, this is something you can do independently. Typically swelling will go down from something like this within 24 hours. It's been that long now, is it better?
You might have a problem that is unrelated to the fingering event. Possibly an infection, a cyst, a fibroid, or something else, that just happened to hit around the same time as you got together with your boyfriend. Tell your mom you're having unusual cramps and see the ob/gyn.
Also, you could possibly have a UTI if his hands were dirty or had bacteria. Do go see a doctor though to rule out any infection.