The 30-year-old has recently returned from a loan spell at Yeovil but is now expected to be out for up to three weeks.
"It was a minor operation and nothing too serious. It was just something that Gavin needed fixing," boss Keith Millen told the club`s official website.
Surplus to requirements at Ashton Gate, Williams will hope to regain full fitness in time to earn another loan move before the end of January.
Source: PA
Source: PA