Poom has dislocated the finger twice this season and this has resulted in inflamed tendons.
Specialists have told Poom that rest is the first option to try and clear the injury. It was rumoured that Poom could have an operation to cure the problem. However an operation at this time would almost certainly rule out a return to the squad before the end of the season.
The Rams now face a goalkeeping crisis with Andy Oakes still injured the only fit keeper at the club at the moment is Lee Grant, who is not 19 until the 27th January.