The rider was taken to hospital after parting company with Lucky One in the Betway Mersey Novices’ Hurdle, but Cobden had initially hoped to make a speedy return.
However, he has been forced to end his campaign early with further checks revealing fractures in his cheekbone that will require surgery later this week.
Cobden currently sits in third in the jump jockeys’ championship, 13 winners behind Harry Skelton and 14 adrift of defending champion Brian Hughes, with the duo locked in an enthralling battle that ends on April 24 at Sandown.
Cobden’s outside challenge has now been ended, but he is focusing on next term already.
He tweeted: “I went for further scans yesterday and, unfortunately, they have shown that I have got a couple of fractures in my right cheekbone. I am having an operation on Thursday, but I am out for the rest of the season (likely to be six weeks).
“Good luck to both Brian and Harry in the champion jump jockey title race. I look forward to hopefully challenging you both again next season and I hope that next season also welcomes people back on to racecourses.”