Sen. John McCain, R-Ariz., suffered a minor tear in his right Achilles tendon, his office said Monday, and will wear a walking boot until he is healed.

McCain received treatment at Walter Reed National Military Medical Center over the weekend for the injury to his Achilles tendon, as well as for “other normal and non-life-threatening side effects of cancer therapy.” The Arizona senator was diagnosed with brain cancer in July.

McCain has since returned to work on Capitol Hill, and took to his Twitter account Monday to lament having to wear the walking boot.

“I can’t tell you how much I hate wearing this boot!” the Arizona senator tweeted, with a photo of himself sporting the boot: