Sentinel 2 imagery is already ortho-corrected and georeferenced. However I wish to know how important it is to correct further and which correction to carry out.
Refer to this answer. It references Landsat-8 but the same corrections (or lack of) apply regardless of the sensor. Generally, if you're doing land cover change detection you will need to apply radiometric corrections at a minimum and possibly atmospheric corrections, but these can be complex. You may also need to consider time of year and other seasonal variations between the image capture dates (ideally the images should be captured at the same time of year to minimise these effects).
It really depends on the types of land cover changes you're trying to detect. You may not need to apply many corrections at all if you're doing is identifying significant changes i.e. de-forestation.