Have what feels like a cyst on vaginal opening, right side. Some pain, slight heat, about the size of a pea, feels swollen. Do I need a doc to treat it?

Bartholin cyst. I would recommend you see a physician. This could be the early stages of an infection in your bartholin gland.
Pea-sized cyst. For a cyst this small, i would just treat it with warm compresses for 15 minutes at a time 3 times a day. If it doesn't get bigger, it will probably go away on its own. If it does get bigger, then you will need to see an md.