Could very well be wrong , but looks like a blister maybe starting to form? Benny had a small one at the tip of his ear that I noticed one night after removing tape. To fix I back taped the post, but left the part that would touch that part not back taped and instead cut a small piece of gauze and taped it there (so that affected part was not touching tape, I also put a little bit of baby powder on the tip of the ear to help with moisture and rubbing). After two posts like that it was gone, but I continue to put a little baby power at the tip of each ear.
Also I have also read to make sure the tape at the tip of the ear is not too tight and if the tape gets any moisture at all to remove as the tape will shrink...