Hi and welcome to Just answer.
Initially, may I know what is the make and model of your machine?
Can you try to remove all your thread (both upper and lower) then remove your needle. Now, turn the hand wheel again if still locked.
The hand wheel is smooth when you are in bobbin winding mode because the needle mechanism is not engage so your problem is in needle mechanism.
Please let me know the result so that we continue to troubleshoot.
Hope this information will be helpful.
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