without contacting the ISP who owns the IP address, its impossible to get a location more accurate than the town/city the person is in. And as even my smallish town has like 50,000 people its not much of a risk.
If you use your nickname elsewhere, ur more likely to be traced using that than your IP address.

Altho, having a publically displayed IP address on a large network is an invitation to be scanned for trojans etc or to have exploits attempted on.
But as long as u got a decent anti-virus, firewall and ur OS is patched up, you'll be safe.