This is a classic of lack of B2/B12.
You need to take a complete B vitamin supplement every day PLUS a B2 supplement, 'riboflavin' every day for a week.
BAD DIET!
More liver, meat and fish.
But with the addition of B vitamin supplements, this usually clears up in 3 days.
My personal experience and UpJohn's vitamin manual.
(I actually study vitamin A)