Chris Bosh -- My Baby's FIRST Miami Heat Jersey

Miami Heat superstar Chris Bosh has a NEW biggest fan ... his brand new baby boy ... who cheered on his famous dad from his hospital room yesterday ... just HOURS after he was born.

Bosh had a helluva Thursday ... with his wife Adrienne giving birth to little Jackson Bosh around 3 AM ... and then having to play in the NBA playoffs against the NY Knicks.

But Bosh made it happen -- hopping on a private jet in Florida and arriving over to Madison Square Garden an hour before the game.

With his son decked out in custom Heat gear ... Chris scored 9 points in the win over the Knicks ... and then hopped BACK on the jet to return to his family ... completing a 2,200 mile round trip in less than 24 hours.