Should I replace the tyre or can I keep going?
It's difficult to tell from this picture, but it looks like the casing—the structural part of the tire—has been damaged, so it's just a matter of time before the tire fails completely.
Look at the inside of the tire. If the damage has penetrated all the way through, I would stop riding on that tire. If it hasn't, you might be able to get away with gluing in a &quot;boot&quot; (a small piece of old tire) to reinforce this spot. But based on this picture, I think replacing this tire is the smart thing to do.