Brief Answer:
It can be inflammation or refractive error.

Detailed Answer:
Hello Madam
Welcome to Health care Magic.

I am Dr. Dadapeer K, an ophthalmologist and I answer health problems related to eye.

I reviewed your history. It seems from the history that you are having pain in left eye on moving the eye, headache and the eye is appearing smaller.
This can be because of inflammation in the eye or because of refractive error.
If you are having symptoms of redness, watering, blurred vision, sensitivity of light... it indicates inflammation. If you are having any of these symptoms please send a photo of the affected eye so that I can confirm the diagnosis and advice you accordingly.

If you are having only blurred vision or diminution of vision thus indicates refractive error and requires treatment by refraction and correction.

Hence I advice you to consult your ophthalmologist for examination and treatment accordingly.

Hope this is helpful to you.

Do write back to me for further questions.

Thank you
With regards

---