Swelling and itching around the vaginal opening after a UTI is common. Antibiotics for the UTI can disturb your normal vaginal bacteria and let yeast overgrow, causing a secondary infection on top of it. Friction from intercourse can also leave the area irritated. It's usually not serious, but it needs a look to tell a yeast infection from the UTI continuing.
Next Steps
Keep the area dry, wear loose cotton underwear, and skip scented soaps or wipes there. An antifungal cream often helps if it's yeast, but have your gynaecologist examine you first to confirm, since you're already on UTI medication.
Health Tips
See a doctor sooner if you get fever, foul-smelling discharge, or the swelling and pain worsen, since that can mean the infection is spreading.