So long as the photo on the card is recognisably you, you will be able to use it. Dive centres don't check C-cards against e.g. passports (and some don't even check C-cards!). If it's only a typo, it's not even worth worrying too much about it, it's not an official document, after all.
However, if it really bugs you, you can get a replacement from whichever PADI office issued the card. Phone/email them first to enquire what's needed (likely just a cover letter explaining the situation, a photocopy of e.g. your passport, a photocopy of the card, and a passport-size photo with your name on the back). I believe the contact info is on the temporary card that you were issued after your course, if you still have it. If not, you can find it at http://www.padi.com, under 'contact us'.
Be warned, PADI may want to charge you for a replacement. Unless you can show that the mistake was their fault (e.g. you have a photocopy of the legibly filled-out PIC envelope), it's unlikely that this charge will be waived. Can't hurt to ask though, PADI are always banging on about customer service and satisfaction... ;-).
Or you can just sign up for the next level of diver training, after which you will get a new card anyway. Just make sure that this time you fill out the PIC yourself, print in block capitals, and take a photocopy before you send it off, so this doesn't happen again.
All the best.