Don't screw up your finger for life.
After an acute injury, the process of inflammation begins.
Cells at the site of injury release chemicals (cytokines) that cause protein strands to be laid down to heal the torn tendon.
Those protein strands are thin and flimsy like a spiders web.
Like a spiders web, those strands are easy to break with any movement.
Over time though (six weeks) those strands are bound together, just like the many strands in a rope or cable are bound together to form one strong rope or cable.
The problem is that with early movement, the ends of the tendon pull apart again, tearing the fragile protein strands.
The body has to start over again.
If too many restarts happen, each end of the tendon seals over in scar tissue.
Only surgery to cut away the excess scar tissue and fixation of the two ends surgically would then result in healing.
But with such extensive inflammation and surgery around such a small joint as exists at the end of the finger, you increase the chance that the joint "freezes" from getting involved in the inflammation - with excessive internal scar tissue freezing the joint movement.
So don't blow your chance at healing by playing tennis. You have to grasp the racquet too firmly to avoid motion.
I gave up playing tennis for 6 weeks when I incurred a mallet finger when I attempted to catch a smashed tennis ball, rather than let it fly into an adjacent court.
That was years ago and I am pleased to have a normal functioning finger.