Don't panic. Be bold.
If you have the mail copy of your resignation letter , just forward it to your new company HR.
Also, forward them the mail which shows the acceptance of your resignation from your present manager.
So that, the new company confirmly knows that you are ready to join them.
Also, you try to keep in touch with the new company HR. Explain them the situation. Always be cool. Convince them .
Finally, try to be patient and cool with your current manager. Agree to whatever he tells to you (like a cat you should behave).
Daily follow up with the present manager for your earlier relieval.
With Best Wishes,