The German took to Twitter to say sorry to the teenage midfielder, explaining that his frustration had got the better of him
Late in the Cottagers' 3-1 Premier League defeat on Saturday, the German was involved in an incident with his young opponent that was not seen by the referee.
However, after reviewing video evidence, the Football Association (FA) decided that Riether had a case to answer and, with a response to the charge due on Tuesday afternoon, the 30-year-old right-back took to Twitter to offer his apologies.
"I want to say I am sorry to Adnan Januzaj. It was very unlike me and I can only say that frustration got the better of me," he wrote.
"I also want to apologise to my team-mates, fans and everyone at the club for the ban incurred following Saturday's match.
"I will accept the consequences of my actions and hope to put it behind me when I return.
"I want the fans to know that I will be working hard to stay fit and will be ready to continue fighting for the club as soon as I am able."