Do you happen to have an older PII / PIII Katmai / Athlon Slot A chip? If you actually borked a piece of the cache chip off, then theres really nothing you can do (unless you have the guts to desolder it and find another one somewhere.....and then solder THAT back on....). What you should really do is buy a new processor. If its a PII, you can get a cheap one in the forums or on Ebay ($30 or less). If it was a PIII Katmai, they are NOT cheap (up to $100 for a 500) and not worth buying a new chip, as you could put together a faster Duron + mobo combo for the same price. If it was an older Athlon Slot A chip, you could go try to find a new one to replace it (maybe ~$50 for a 700) or you could do said duron + mobo combo.
if you really wanna splurge, you could spend a couple hundred and get a whole new setup............and leave your wallet possibly bare.