An interesting and unusual question! Battlefield acupuncture is not really within the usual scope of traditional acupuncture, and derives mainly from the work of Richard Niemtzow and his colleagues in the last two decades. This 'expert' recalls seeing one of his first major presentations of the technique at a BAcC conference in the early 2000s, and there was no mention of any specific cautions over and above the safe and hygienic methods we all use anyway when inserting needles.
The best steer we can find is from advice given to people who have had body piercings. These are much larger and if there was a risk then this would be massively amplified by a more substantial piece of metal. The only real caution we could find was that it would be better to avoid using a sunbed in the first two or three weeks after a piercing has been inserted in order not to aggravate the wound. We strongly suspect that this would be the best advice we could offer.
Of course, the person who will be best equipped to field this question will be the practitioner who inserted the needles. On the assumption that they have trained in the technique rather than self-taught by the use of books and videos, it is highly likely that they will have been alerted to possible risks like this. However, we have also searched the adverse events databases and haven't found any reports to suggest that there is a risk from using a sunbed after acupuncture.