Hello! :-) We need a bit more info, like how long has it been (in hours) swollen? Is it sore/rash-like/red? Did you have rough sex, or do something differently during sex? I know it can be embarrassing to give so many very personal answers, but we are used to that here, so no worries... there is no way any of us would tease you about it, and we are glad you came to us for help! :-) Blessings - Blu
Any swelling down below no matter how it is caused is called Vaginitis.
I suggest you book an appointment with the doctor to get this checked out and a swab taken. Depending on what the results are, the doctor will prescribe the appropriate medication, either an antifungal cream or oral tablet for fungal problems like Thrush. Or an antibiotic if it is caused by a bacterial infection.
Your partner may also have to be treated at the same time.
Do not use soaps or any bubble baths or any feminine sprays down below. And don't wear manmade underwear (pants), this can aggravate the condition further.
If you use condoms, you may be allergic to the ones you have used. You can get different ones and also non-latex ones. If you go to the family planning clinic when it is open you will be able to get to get contraception (condoms) and lubricants for free. You will probably already know that the doctor will prescribe other forms of contraception by issuing you with a prescription.
This might be minor trauma. If you have 100% pure clear aloe vera, put that on it. If you have Vagisil, use that. Or just cleanse with a mild soap like Dove and see if it goes away.