But, I will like to know if there can be any way someone can check the validity of his paper wallet private key correponding to his address.
You can simply install Electrum on an air-gapped computer, import your private keys and check generated addresses.
I am thinking of Iamcoleman, but it is possible to use such to test the validity?
If I'm not wrong, iancoleman can be used only for getting private keys and addresses derived from a seed phrase. As the website's title says, it's a Mnemonic Code Converter
I don't think you can enter private key and get address.