about 5 months ago i got a big blister in corner of my mouth which presumed was a coldsore, first one ive had. after 2 weeks it went away. But then i had a Red blotch in the same corner of mouth on the skin just comming off the corner of my lip. sometimes it fades so its really slight and not really noticeable and sometimes its worse and can clearly see i have a red mark in the corner. But it never goes away.. its been about 5months.. i tend to put Vaseline on it before going to bed and that seems to keep it faint.
what is it?