Originally Posted by 6SPD_soul
It's risky when you get into the shoulder of the tire, and really if it's anywhere near the sidewall you probably won't find any shop willing to do it, or you find a place like Flylow mentioned and they'll tell you it's a bad idea and then do it for you. It's a really easy job to do yourself, just take the tire off, deflate, get nail out and put in the patch, reinflate.
If you've got the money to spare I'd recommend replacing the tire, if money's tight patch it and hope for the best.
if its not that bad you dont even need to remove it and patch it... just get a DIY tire plugger kit... in and out in less than 2 mins and you can leave the tire on (i call them sticky worm kits)