You should cancel-amend Purchase Invoice to change the price. one cancelling, invoice will be unlinked to payment entry. you can later link them both via Payment Reconciliation Tool.
Since the question itself says 'mistake in entering price" (purchase invoice is entered based on Bill received from Supplier, so this seems to be an oversight). A mistake could be corrected by ‘Cancel’ document and then ‘Amend’ for price changes.
After making the changes >> Save and Submit. The revised doc number would be linked to the original purchase invoice document for easy reference in future,