might be the King, but he thinks he's getting royally screwed over when it comes to officiating ... 'cause the Los Angeles Lakers superstar just unloaded on refs for not calling a foul after he suffered a bloody arm scratch during Sunday's game.

The play in question went down when LBJ drove to the basket in the third quarter of the Purple & Gold's 134-110 home win over the Portland Trail Blazers ... but instead of two points, he ended up with a few cuts on his right bicep at the hands of opponent

Scoot Henderson.

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James was patched up with an ointment and continued the game ... finishing with 28 points, five rebounds and five assists on the night.

Despite the solid outing and a team win, James is clearly still upset about how the sequence played out ... 'cause he had a message for the officials Monday afternoon.

"[Zebra] look right at me and said, 'I didn't see a foul!'" Bron said on Instagram. "Man what!"

"I give up man."

It's going to end up being a pricey post for the King -- the NBA has strict rules against publicly criticizing referees ... and a fine is likely on the horizon.

But considering the guy is a billionaire, LeBron probably doesn't care.