I have numbness in my thumb after hand operation. is this normal?

Not usually: If you had numbness to begin (such as carpal tunnel syndrome) and the surgery is to relieve that problem, it may take months to fully resolve; if you never had numbness until the surgery: no, that's not normal and you should tell your surgeon so a proper diagnosis can be made.

Numb after surgery: Immediately after it is quite normal. If it doesn't resolve within 3 weeks, it may take even longer and could be permanent. This depends on the nature of the injury and/or the surgery and is best discussed with your surgeon.