Hi,
Welcome to ehealthforum.
HSG procedure has high chances of making endometrial cells spill out along with the dye. The possibility of endometriosis cannot be ruled out. If your symptoms were present since before the procedure, then the procedure alone cannot be blamed for being the cause for endometriosis. If the symptoms have started/developed purely after the HSG procedure, then it can be held responsible for the endometriosis growth or worsening.
Take care.