It means an uncertain decision that can't be made mechanically. It asserts authority: "Nobody can be sure, but it was my job to make the decision, so I made it." I think the literal reference to sports--perhaps specifically to baseball. In U.S. usage, a decision by a referee is often referred to as "a call." A baseball umpire "calls balls and strikes"--announces whether a pitched ball was inside or outside the "strike zone." A "bad call" means a mistaken or incorrect call. A "judgement call" is a call requiring human judgement on the referee's part. In theory, a machine could determine whether or not a pitch was inside or outside the strike zone, by using laser beams to outline the strike zone, perhaps. But there are other calls that are not purely mechanical. For example, deciding whether or not a pitcher has "balked" requires the umpire to judge the INTENT of the pitcher--whether or not the pitcher is intentionally trying to deceive a runner.

It means to make the best decision based on the facts you have.

Basically it means you had to make a quick decision based on your own opinion.

"Boo Boo Bear" is the brand name of a bear-shaped item ,filled with gel, that is frozen and then used to treat minor injuries where ice might help. A "boo boo" is "baby talk", or words used by and for young children. It means "a small injury."