Player B forgot to track point Player A has a note on points how the game goes?

The game proceeds with the point corrected. If Player A's note lets the judge determine the correct score, and no more than a full round cycle has passed since the miss, the appropriate player's score is incremented to the correct total (Tournament Rule 702.3.b.1). Notes are legitimate evidence for that determination.

Once a full round cycle has passed (i.e., the turn player's next turn rolls around), the point can no longer be fixed and play just continues at the tracked score (702.3.b.2). Either way, a score discrepancy must be announced to all players immediately when noticed — per TR 415.3.b, if it can't be resolved easily, call a judge. Note this only covers Conquer/Hold points; points from card triggers like Ahri, Alluring are missed triggers and aren't given back (702.3.a).