I used to hold left hand tightly while playing violin, i have wrist pain now.how can i reduce pain?can i continue my violin practice?

Rest for now: An ounce of prevention... Best not to hold it so tight. I would rest it for a few days, perhaps warm soaks and an anti-inflammatory agent like Aleve (naproxen) should help dramatically.

Wrist pain: You may have carpal tunnel syndrome. Its best to rest it until the pain is gone (7-10 days). Use the naproxen twice a day, ice pack to wrist for 20 minutes 3xday. Consider getting a wrist brace. Failure to treat this condition could end your violin days for good. See an ortho doc for a good exam.