Was kinda dry during last sex encounter. 3d later, vag still feels swollen, inflammed, and slightly itchy. No risk of stds. Is it yeast?

Irritation . It can be just irritation from friction during sex if there were not enough lubrication, for yeast or other type of vaginosis watch for any discharge or abnormal odor. If the inflammation does not goes away after 5 days the i will consider possible yeast infection.
Dry vagina. Yeast is always a possibility but i would think your major problem would be discharge. If you were dry during intercourse then this may have caused irritation. I would suggest using a moisturizer such as KY jelly before intercourse.