Hello and welcome to HCM,
A painful area on left side of the labia which burns on touching can be due to a number of causes.
, infected cysts, etc can be the cause of these symptoms.
A clinical examination is required to look for any localized lesion in the introitus.
Associated swelling of the vaginal wall can be due to congestion during pregnancy
However, it can be secondary to the infection/ inflammation of the introitus.
Infected cyst can be surgically removed even during pregnancy.
Thanks and take care
Dr Shailja P Wahal