On this particular design for the
Lincoln Memorial cent, that area is a little more defined that other years. I think you are just seeing the design. It's always good to look at a nice example of the year/mm that is in good condition for comparison, sometimes you've just never noticed certain things. There could also be some raised area due to plating disturbances. Here is a pic from PCGS, with a close up of the area you have in question.

-makecents-