If it's a serious question, a couple of serious questions in return:
Do you want to keep the piercings? And are they already healed?
If they're not already healed and you take the jewelry out, you'll likely lose the piercings. Nipples are highly vascularized and close really quickly.
If they're healed and you take the jewelry out, you might still have issues putting it back in when you get home - again, highly vascularized, close quickly.
I'd say, if you're currently having trouble with the piercings, don't go out at all. You've got open wounds that are already giving you pain, and you don't need to deal with that on the trail, whether or not there's still metal in them.
If they're already healed or are healing well, tape them down securely to reduce chafing and keep gunk out, carry some alcohol and/or antibiotic ointment in case they give you trouble, and leave the jewelry in.
They're no more likely to cause an infection than any other skin break (which *never* happens in the woods ::rolleyes:: ), and they're covered by clothes.
I'd also suggest reading the rec.arts.bodyart FAQ on piercing, as that will give you information about your piercings it sounds like you should have:
http://www.faqs.org/faqs/bodyart/