It shouldn't affect you much. "Board-eligible" is enough for privileges just about anywhere. I don't know if any carriers require subspecialty board certification or board-eligibility in pain. It doesn't look like it to me. As for referrals, doctors understand about being recently out of training and not having boards yet.
The only snag might be advertising. The state board might have problems if you're not certified. Sometimes it's a matter of wording. They might not allow "specializing in pain management" (if you're not boarded you're not a specialist) but they might tolerate "pain management". I have seen the Texas board reprimand people for advertising that they specialize in "invasive pain management" since there is no such specialty. OTOH, TMB is a special case because they have been so draconian that TX docs have revolted and demanded an investigation into their practices.