The 52-year-old, who has been a special for more than 15 years, was hit by a passing car while attending the scene of a separate collision on the Wolverhampton Road just after 10.30pm last Friday.
The officer, from the Force Support Unit, suffered multiple fractures to his leg and remains in hospital in a serious but stable condition.
Special Chief Officer Mike Rogers said: "I visited Resham this week and he is in good spirits.
"But he is currently undergoing extensive treatment and we believe that will continue for some time.
"This incident does clearly illustrate the risks we, and all the policing family, face in our role of protecting the public we serve.
"Our thoughts and best wishes go to him and his family who are helping support him in his recovery."
The 59-year-old driver of the vehicle was arrested at the scene on suspicion of dangerous driving. She has been released under investigation while inquiries continue.
It is the latest incident where a West Midlands Police officer has been injured recently.
In September an officer was injured in a hit-and-run in Coventry and in August Pc Gareth Phillips was badly injured when he was run over by a hijacked police car in Birmingham.
Anyone with information about the Oldbury incident is asked to contact police via Live Chat at www.west-midlands.pnn.police.uk between 8am and midnight or call 101 anytime. Quote log number 2788 of 8 November.
A JustGiving page has been set up in aid of Special Constable Nahal. Anyone who would like to donate can visit justgiving.com/crowdfunding/sc-nahal?utm_term=jammDd7jM