The Balkan nation ran Argentina close in their Group F opener, but fell to a 2-1 defeat after an own goal from Sead Kolasinac and an indivdual effort from Lionel Messi, despite replying late on through Vedad Ibisevic.
Pjanic acknowledged that a win in their clash with Nigeria was now essential if they are able to progress beyond the group stages in their maiden World Cup finals and stressed he would be satisfied with nothing less than the chance to reach the last 16."This is important, a key match," the 24-year-old told a press conference.
"We are raring to go. We can hardly wait for it. We know how important it is. If we lose, it's over. We will not let that happen. We will fight. It is an important match not just for us players but for the whole country.
"We have certain players who want to bring our national side to the very top. I play for the national side to win. I'm not satisfied with losing.
"This World Cup would be greatly disappointing if we got stuck in the group. This mentality is right. We are never satisfied. After the Argentina game, who are better than us, we were disappointed. It's the only way to make progress."
Pjanic also hailed the impact of Muhamed Besic after the 21-year-old's performance against Argentina."Muhamed has made a very good impression on me," he continued.
"He is a high-quality player, he means a lot to us. We are all satisfied with his efforts, the will he demonstrates, how he plays. I think that we are a much better team as a sum of all our parts and not as individuals."