After the final attempt from Marcus Smart bounced out to seal the 100-99 final, Hield kicked the ball into the stands in excitement.
According to Shams Charania of Stadium and The Athletic, the guard has been fined $25,000 for his actions.
Everything was going right for Hield until that point, totaling a season-high 35 points on 14-of-24 shooting, including 7-of-12 from three-point range.
He especially came through in the clutch with some big shots late:
It led to the team's biggest win of the season over a Celtics team that entered the day with an NBA-best record of 10-1.
It has already been an up-and-down season for Sacramento, which started 0-5 before winning five of the last seven games. Hield had his own problems with some terrible shooting games in October before rebounding with 22.7 points per game in November with at least 20 points in six straight games.
After signing a four-year, $94 million extension last month, 26-year-old should be able to handle the latest fine.