I don't know what the blister is from but you need to start drinking a lot more water. dry cracked lips need lots of water to heal. The blister may be a cold soar and go to any drugstore for a medicated lip balm.
From your symptoms it looks like cheilitis lips which may have been triggered by an allergic reaction. Certain medications, like those used to treat acne and allergies to cosmetics and skin-care products, can also contribute to dry and irritated lips.
Other possibilities are Crohn’s disease (Granulomatous cheilitis, a lumpy swelling of the lips, can be a symptom) and sjogren’s syndrome(an autoimmune disorder in which immune cells attack and destroy the exocrine glands that produce tears and saliva).
Please consult a dermatologist and discuss these possibilities. Till then keep your skin and lips moisturized and take adequate fluids throughout the day.
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 to your advice. I drink plenty of water now and keep my lip moist all the time.I will book an appointment to the Doctor tomorrow and will let you know the diagnosis later.Have a great day! cheers