You can check if an SSL certificate matches a Private Key by using the 3 easy commands below.
For your SSL certificate: openssl x509 -noout -modulus -in <file>.crt | openssl md5
For your RSA private key: openssl rsa -noout -modulus -in <file>.key | openssl md5
For your CSR: openssl req -noout -modulus -in <file>.csr | openssl md5
