TMI: Swelling after sex?

This is a weird question, but tonight my boyfriend and I had sex after not having it for a few weeks (we’ve been broken up.) sometimes if I’m not wet enough I know my vagina could swell, (it’s on the outside) but tonight the swelling is so bad that it hurts. I didn’t feel any discomfort until we were done, but it’s bad. Earlier in the night we had given each other back rubs with some of my hemp lotion, so maybe some of it got in me and caused an allergic reaction? I guess I’m just wondering if anyone might know what’s going on, and now to prevent this in the future. Thank you.