I have deleted a keyboard language on my pc which I thought is the hindi language keyboard. Then I turned off my pc. When I turn on my pc I found that I have deleted the wrong language and I could not enter the password to unlock my pc. Please help.

Try another admin account for login, then re-add your language back.
If you don’t have other account for login, system restore is a method.
I find out a similar case, hope it can give you some ideas.
Cannot login my windows 10 computer cause the language of the keyboard changed.
https://answers.microsoft.com/en-us/windows/forum/windows_10-other_settings-winpc/cannot-login-my-windows-10-computer-cause-the/ab1b3b6c-bfcd-49f9-b16d-762a47959e22?auth=1

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I have an very awesome answer and it really worked. Run system recovery on your pc this will not affect your files and will help you unlock your pc. This happened with me also and I run system recovery it's now resolved it's very good awesome I am writing this just after doing recovery I loved this method thank God Hoooooooooo.Remember run recovery on the date you have not changed the language you will be very happy. It takes very less time do it.