Rangers reliever Sam Freeman plunked Sandoval with the 94 mph heater, causing the third baseman to collapse at the plate in pain.
Red Sox manager John Farrell and a trainer rushed onto the field to check on Sandoval, aiding him to his feet and helping him as limped off the field and into the clubhouse.
After the game, Farrell said that all scans of Sandoval's knee came back clean and that he was sore as a result of being hit.
"You take mid-90s off the knee, it's going to be a little sore," Farrell said. "We'll check him when he comes in [tomorrow]."
Sandoval concurred, noting that it wouldn't be a long-term injury and that he would see how it responds in the coming days.
"So far so good. Nothing broke, that's the good news," Sandoval said. "It's going to be sore for a couple of days.
"I don't know how I'm going to feel tomorrow. I want to be back."
Tuesday night was the third time this season Sandoval has been pulled from a game with an injury.
The third baseman suffered a bruised foot on a hit by pitch against the Washington Nationals on April 17, along with being pulled from a game against the Toronto Blue Jays on April 28 with neck soreness felt on a diving play.
Sandoval went 1-for-3 at the plate in Tuesday's game before Brock Holt came in to pinch run for him after the HBP.
Farrell also explained the visit he and a trainer made to Hanley Ramirez at second base in the fifth inning after an awkward slide. Farrell said that Ramirez jammed his left leg while making the slide, narrowly beating the throw from the outfield for a double.
Ramirez stayed in the game and doubled again in the seventh before being replaced defensively in the bottom of the ninth by Jackie Bradley Jr.
"Just wanted to get him off his feet in that final inning," Farrell said.