tendons are actually rather easy to cut, my mate had the same thing, got told nah you'll be fine, was on the middle finger, knuckle that joins to the hand, copped a metal strap to the back of it, they just stitched it up, said your all good, 3 days later he was still in that much pain i told him to go back, went somewhere different where they checked it, tendon was fully cut, even doing all the rehab the finger is still shite in terms of range of movement, makes it pretty hard for him being a sparky and all, but i think going back to work too soon didnt help, but thats what happens when work cover stops paying.
i would suggest doing everything they tell you, cause if you bugger around with it, its not gonna sort itself out.