I have got a single small blister in upper inner left eyelid since yesterday..what could be the reasons and remedies?

Many: A single small blister in the eyelid has several causes. Most frequently, it can be due: a blocked gland, like a sweat gland an infection like herpes/zoster (most often this will be associated with pain or tingling and prior history of cold sores). Since there is a good treatment for herpetic infections that can reduce recurrence, the blister should be examined by an ophthalmologist.

Warm compress: It's probably a sty, a moderately inflamed "sweat duct" in the eyelid. I tell my patients to get a damp wash cloth and pop it in the microwave for 30 seconds. Test it on your wrist to make sure it's not too hot. Place warm compress the closed eyelid for about5-10 minutes and re-heating as necessary. If it does not get better in a week or gets worse go to your eye doctor.