Since it is at the edge of the lens it might not affect the images taken in bright sunlight as the aperture will be stopped down considerably. As the light source gets dimmer it may start to act like a stuck aperture blade, lessening the exposure.
Depending on the construction design, you may be lucky in that the front half of the casing will separate from the rest of the camera innards. Look for screws inside the battery compartment, and inside the film chamber, then there will likely be snap hooks along the edge of the casing. Squeeze it some to get those to release. There may also be a lever connection between the sliding lens cover and the interior construction, so first lift it a little bit and take a peek inside with a flashlight.
If everything inside is hung off the front casing, then that complicates things. But this style of camera usually has the innards attached to the back casing, or a center bulkhead.
PF