Hi,
I've had tendonitis in my wrists and unfortunately it took months for it to heal (and with occasional recurrences). I wore splints which I got from my doctor and took ibuprofen to help with pain/inflammation.
I got my tendonitis because of work (in a library). As far as exercise, I had to modify some of the things I did. For example, when doing push-ups I found it was helpful to grasp onto dumbells in order to keep my wrists straight (or else I put the weight on my fingers and my palms off the floor, thus keeping my wrists straight).
Where is your tendonitis located? If you go to the doctor, I would guess that your treatment would be similar: immobilization, anti-inflammatories, and modifying or stopping the culprit activities for a while.
Hope that helps. Feel better soon!