The private key is secured by a password.
How strong is this password?
I deleted the file on iCloud just a few minutes later.
Doesn't matter. Nothing is ever really deleted from the cloud. There will be an unknown number of back ups of your data still stored on various servers around the world.
What advice could you give me now ?
You definitely need to create a new cold wallet and transfer your funds to it. If your password is weak, then you need to this immediately.
I am also curious how you accidentally exported and uploaded the private key from what you are calling a cold wallet. A cold wallet should be on an airgapped computer without an internet connection. To accidentally upload it you would have had to export it on your airgapped computer, copy it to a USB, transfer it to a live computer, and then upload it, all without realizing it was the wallet file and not the xpub. It sounds like you are using a hot wallet, not a cold wallet.