That is a very interesting problem. Often bilateral swelling is noted in the head, but often the globes are involved. Things to consider are abscess, tumor, infection/inflammation, or any other mass displacing pathology. Other things may reveal that the symmetry is a fluke, as in an injury to both sides from one event (like biting on a stick so to speak).
The course of action to take if this persists is to take to the vet for workup, which may include bloodwork, radiographs, ultrasound, CT scan, ect. Obviously not all imagine techniques would be used, and what is used may also be dictated by what is available to the DVM.
Things that would make your vet visit more urgent are
1)other symptoms appear, like anorexia, lethargy, labored breathing, regurgition, loss of coordination, tremors, seizures, star-gazing ect.
2)the "bulge" increases and/or shows no signs of improvement
3)either of the above occur and the snake is in pain or otherwise suffering
4)the bulge opens into an ulcerative sore
Good luck, as of now I wouldn't yet panic 