Best way to fill crack at base of sink drain?

[Patrick M.]

So I re-installed a sink tonight that had a hard-to-remove 30-year old drain on it. I'm adding a new faucet. In order to get the old pipe off, I had to use an oscillating tool/blade. While I was cutting, I made a few tiny sliver cuts in the circle at the base of the drain. I finished the install and ran the water, only to find that the rubber washer above the lock but can not make the seal because of these slivers. The damage seems truly small, so I intend to fill the cracks, let it dry, and carry on. Here's my newbie question: what do I seal it with? Concrete floor patch? Something else? What do you recommend? Picture attached. Thanks in advance for any and all advice!