Hi!
First of all, congratulations for your excellent result!
Usually, middle name is not a very essential part of the name in documents. You should always cross-ch eck before submission.
What you can do right now is to mail this problem to the email id of concerned authority. If your other details in the form (e.g. address, phone number, details of parents, etc.) are correct, then you can ask authorities to do the correction.
They will verify all the information from your marksheet and Aadhar/PAN card. You need not worry.
It may or may not be a tedious process. If your middle name is mentioned correctly in your marksheet and other documents, then it will be easier to do the correction.
Best wishes!