Ah. Tenosynovitis. Yes, I'm quite familiar with this ailment, having experienced it a couple of years ago—around my birthday, no less. Make sure to have it evaluated by your medical provider, as it can lead to complications when left untreated.

Be sure to rest and avoid any activities that may have caused or worsened the tenosynovitis, and wear a brace or splint to reduce stress on the affected tendon. Heat or cold therapy may help reduce discomfort, and some cases may benefit from corticosteroid treatment under medical supervision. You may be prescribed antibiotics if an infection is suspected.

The most important thing you must do to aid your recovery, after seeing your doctor, is rest. I wish you well and a speedy recovery.