Firstly,It can be due to vit B deficiency.Take some vitamin B complex for some days and see if your symptoms improve.
Secondly it can be due to cheilitis. Avoid licking the lips as saliva evaporates quickly resulting in them being drier than before. Drink plenty of water and take multivitamin supplements and do not apply lipstick or other cosmetic products for some days. Use a humidifier to moisturize the air in your home and apply shea butter or Vaseline on your lips. If a week of compresses and emollients don't do the trick, you can add over-the-counter 1 percent hydrocortisone ointment to your regimen.
It is very difficult to precisely confirm a diagnosis without examination and investigations and the answer is based on the medical information provided. For exact diagnosis, you are requested to consult your doctor. I sincerely hope that helps. Take care and please do keep me posted on how you are doing.
Thank you so much for the reply! The dark spot itself is gone ... but my lips get painfully dry and flaky still. So, I will definitely try taking Vitamin B complex. I stopped taking multivits but I can get back into that as well.
I also read somewhere that it could be from hormonal changes & around the time the dark spot cropped up I had started taking birth control again ... might that have been a cause as well?
I started using Vaseline earlier in the week & that has really helped! There's a complete difference I can't remember the last time my lips were this soft!
I really appreciate you your response & I will keep all of this information in mind. I will also keep you updated. If things turn around again though, I will see a dermatologist.