You are out of luck. A passphrase protected encrypted private key means you have to guess it and with the high entropy of a typical passphrase it will be very difficult. Granted if you have a rough idea of what the passphrase is, you can write a script to try to brute force it (e.g., it was something like 'correct battery horse __' and subject to a dictionary attack).
This is the whole reason you put the passphrase on the private key. (Granted I usually remove the passphrase from my SSL private keys on my server for convenience restarting apache/nginx; though leave them only root readable; figure if someone got to root they can install a keylogger and grab my passphrase anyhow).
EDIT: I should add in principle you could get at your private key if you break RSA (solve the problem of factoring the modulus N the product of two ~1024 bit prime numbers that's in the unencrypted public key; which would let you quickly regenerate the private key) or the passphrase encryption mechanism (typically DES3) to recover the private key. However, if you could do either then anyone else could as well, which would not be a good situation. Also, unless you have made fundamental breakthroughs in number theory, computer science, or developed a quantum computer it is prohibitively expensive to brute-force break RSA (like a million computers going for a million years would have under a 0.02% chance of breaking a 2048-bit RSA key).