To be fair, the production was utilizing a "controlled explosion" while shooting. Regardless, an official update from the film's Twitter page explained that the explosion caused damage to "the exterior of the 007 Stage."
Fortunately, no one was seriously injured on set, although a crew member did sustain what is being described as "a minor injury."
Read the official statement below.
During the filming of a controlled explosion on the set of Bond 25 today at Pinewood Studios, damage was caused to the exterior of the 007 Stage. There were no injuries on set, however one crew member outside the stage has sustained a minor injury. pic.twitter.com/8O9tOgwMYK— James Bond (@007) June 4, 2019
Assuming the entire movie doesn't implode before then, Bond 25 is still slated for release on April 8, 2020.