"It's a bit stressful, especially for my family in England. But I will keep my head held high because I have done nothing wrong," he said in a press conference broadcast on Toulon's website.
"I know that everything will soon be sorted, that I will be able to forget about this and come back stronger."
Toulon have issued a statement insisting the result was caused by approved painkillers and anti-inflammatories prescribed for back pain.
The French club stress that the 26-year-old "has absolutely not taken any illegal substance to improve his performance" and that the morphine is a natural by-product of the painkillers.
According to reports in France, Armitage will appear before the FFR anti-doping commission on August 21 and has been provisionally suspended pending the hearing.
Toulon's statement read: "Before the game, Steffon Armitage took two tablets of paracetamol codeine, a medicine strictly authorised by the French Agency for the Fight against Doping (AFLD).
"Having suffered with back pain in the week leading up to the game, Steffon Armitage was given anti-inflammatories as well as paracetamol codeine (two to four tablets per day) for these pains. All of the medicines administered are authorised by the AFLD.
"The presence of morphine in Steffon Armitage's urine sample is explained by the fact that 10% of this medicine (paracetamol codeine) is converted naturally into morphine."