Don't do anything yourself. Any attempt to seal or otherwise protect the damage will make the real repair more difficult, more expensive, and probably more obvious.
Unlike Martin guitars, the finish on those old Gibsons is notoriously thick and brittle, and very prone to cracking all over the instrument. Neck resetting is potentially more traumatic than normal ambient heat/moisture variations, so it's not uncommon to see this kind of finish stress in the heel area, especially down at the bottom where the heel is more flexible.
Most of the time there's no structural need to repair the finish but it can be filled to be less objectionable looking. Likewise, it can be left as-is for a long time before addressing the cosmetics.