Swollen and itchy vaginal opening and canal

I’ve had some rough sex but it wasn’t until 3 days later that my vaginal opening is swelled up and both my vaginal opening and canal are itchy?

Why?

I thought it could be an STD but we used condoms...

I thought maybe it was because it was rough.. but to feel like this 3 days later instead of right away is weird?

Any advice, what is it?????