It happened at Horizon Family Medicine in the 200 block of Butternut Lane.
A man inside the office waiting on his appointment was able to get out of the direct path of the truck, but was taken to Johnston Medical Center for his injuries.
The driver, 71 year-old Billy Parris, told ABC11 that he wears a brace on his ankle, and his foot got lodged on the gas pedal which caused him to tear through the office.
Parris said he feels terrible, and added that he has a very good driving record.
Meanwhile, officials said the building has been declared unstable until further assessment by engineers.