What could cause soreness on my outer labia?

this morning when i woke up i had what felt like muscle soreness on my outer labia and surouinding areas. i figured it was just because i had to urinate and figured it would go away shortly. unfortunetly ive had it all day today. i just ended my period (as in i took my last pad off this morning) im thinking it could have something to do with it. i have not had since my begining of my period (more than one week ago) and i donot have any stds (ive been tested and so has my partner, we are eachothers first and only partners) it doesnt seem to be serious, nor is it really painfull. honestly it feels the same as the soreness you get when you stand on your feet all day. (which ive also gotten today because its been uncomfortable to sit for periods of time). just wondering what this could be caused by.