I've had herpes on my nipples - but not from b/f. I never did work out where/how I got it - I was about 27 and not in a relationship at the time. Very sore though - my boobs felt like they were on fire and needed to be "supported" all the time - I'd probably got a secondary infection, although it wasn't mastitis (which I've had since, so know the difference!). It was over the Easter weekend, so it was ages beofre I could get to see a doctor.
GP wasn't much help - gave me some antibiotics I think. It was my GP best friend (at the time newly qualified) who diagnosed it (initially over the phone! - but she did see the healing scabs for confirmation) and said that one of her friends (also newly qualified) had just seen her "first" case of "nipple" herpes.
I'd never had cold sores, so that's maybe why I'd ended up being susceptible to it. The virus may have been dormant there for some time.
I don't know how old you are Lumo, or whether you've had cold sores before (if so, as someone said, your nipples are safe, as the virus recurs at the initial site), but if you've not had cold sores, it might be worth checking with your doctor.
I've had two minor recurrences, easily treatable with Zovirax or similar - and fortunately both before I had ds and was breast feeding him!