Colleague gaining majority credit for largely my figures/analyses in their scientific poster
If this would have been a paper, Jim's doing would certainly have been unacceptable. As we are talking about a poster, I could imagine that Jim had no bad intentions. Given that you come from two different disciplines, you are probably not directly competing in terms of scientific merits, and you could both greatly profit from collaborating further in the future. 

In the past I always tried to resolve these kinds of conflicts on the lowest level possible before escalating it to the professor / PI. This helps to keep the work environment poison-free and often resulted in surprising insights on both sides. More often than not people do not have bad intentions. Maybe he considers these figures as a team effort by the two of you. Maybe you are overreacting. In these cases a discussion from face to face often helps to sort things out. 

I would probably talk with Jim and ask him why he did not ask for your permission to use your figures. Maybe also ask him how much, in his opinion, were your and his original contributions to the poster. If he considers your input as important, you could also argue that your contribution helped him to receive the price. I would certainly try to discuss the terms of your future collaboration.

Only if that discussion is not fruitful I would go to the PI and explain the situation.